2018 GLS550 - M278 Very Weird Misfire Issue, Help Needed!
12-17-2022, 11:15 PM
#1
Junior Member
Thread Starter
2018 GLS550 - M278 Very Weird Misfire Issue, Help Needed!
Dear Forum Members,
I used to read MB World forums for years but this is the first time that I feel hopeless and need help...
I have a 2018 GLS550 and around 20k miles, a very weird misfiring problem started. This is what happens:
- Sometimes (30-40% of cold starts), engine starts with immediate misfiring at cyl 8 after cranking, check engine light blinks and stays on, turning off/on does not help, after driving for 2-3 mins and engine gets a bit warm then I turn off/on the engine, everything turns back to normal, car runs perfectly smooth with all cylinders on, no performance issues. Even sometimes, check engine light goes off too!
- The main problem is the misfiring when driving. A very hard shaking starts if I drive at high gears (6-7-8-9) with high load (more than 50% of throttle) and engine rpm between 1,800-2,200 rpm. Under these conditions, an immediate shaking starts (not everytime but 60-70% occurrence), check engine light starts blinking and stays on, engine control unit shuts off the misfiring cylinder and everything comes back to perfectly normal if I turn the key off/on and restart the engine. When I check the fault codes, I see 100% cylinder 8 misfire and 75-80% of the times cyl 7 and 6, and very rarely cyl 1 and 4.
To overcome this very annoying problem, I tried these:
- All spark plugs have been replaced, ignition coils replaced, nothing changed.
- All injectors sent to Bosch center, cleaned and tested, reinstalled, nothing changed. If I change the position of the injectors and recode them for new locations, still the same old cylinders misfire. Nothing moves with injectors.
- I opened up the engine wiring harness top section, checked and rewired all injector/ignition coil wires, common +12V and ground points. Nothing changed.
- Cold compression test done. All cylinders are around 215-220psi and above, very very good. No problems seen.
- All 8 cylinder tops and combustion chamber checked with flex camera, cyl 8 has more carbon deposits on the piston than the remaining 7 but nothing seems severe. I removed the complete intake manifold, cyl 8 intake port seem more CLEANER than the other 7 but all of them shows heavy carbon deposit, more or less. SO I decided to clean the intake ports and valves. With brake cleaner and thinner, I removed all carbon deposits from the ports and valve bodies. Problem is still there.
- I replaced all 4 knock sensors, nothing changed. If I drive the car with knock sensors unplugged, the problem is 90% goes away but performance goes significantly low, naturally.
- I test drove the car with Xentry connected, low/high fuel pressures, intake and boost pressures, engine temp, 4 camshaft angles etc all values are in the range. When I increase the load and start the shake/misfire, I see cyl 8 and cyl 7 misfire counters goes up like crazy and eventually engine computer shuts off cyl 8 and sometimes 7 too.
- Finally I tried STP intake valve cleaner fluid to clean the possible remaining carbon deposits (an experienced MB mechanic told me M278 engines are very sensitive to intake valve carbon deposit), no help.
I have ZERO performance issues, car literally flies if you push hard on high rpm's, no smoke, no hesitation. Throttle response is very very good. If you go over 2,200 rpm and floor it, car is like a rocket.
Under this circumstance, I think the engine is good mechanically. I am considering to change the engine wiring harness thinking about my past experience on my ex Ferrari 599GTB, showing 'transmission failure - hydraulic pump pressure low" error and putting car to neutral which makes car non-driveable for 5-10 mins and comes back to normal until next occurrence in maybe 1-2 months. I saw many similar 'mystic' problems caused by wiring harnesses.
Last note: I drove a 2013 GL550 some years ago, that one was showing similar cold start misfire thing but I discovered a service bulletin about it, reprogrammed the engine computer and problem solved forever. This time, there is no such solution
Any other experiences/comments on this mystery?
I used to read MB World forums for years but this is the first time that I feel hopeless and need help...
I have a 2018 GLS550 and around 20k miles, a very weird misfiring problem started. This is what happens:
- Sometimes (30-40% of cold starts), engine starts with immediate misfiring at cyl 8 after cranking, check engine light blinks and stays on, turning off/on does not help, after driving for 2-3 mins and engine gets a bit warm then I turn off/on the engine, everything turns back to normal, car runs perfectly smooth with all cylinders on, no performance issues. Even sometimes, check engine light goes off too!
- The main problem is the misfiring when driving. A very hard shaking starts if I drive at high gears (6-7-8-9) with high load (more than 50% of throttle) and engine rpm between 1,800-2,200 rpm. Under these conditions, an immediate shaking starts (not everytime but 60-70% occurrence), check engine light starts blinking and stays on, engine control unit shuts off the misfiring cylinder and everything comes back to perfectly normal if I turn the key off/on and restart the engine. When I check the fault codes, I see 100% cylinder 8 misfire and 75-80% of the times cyl 7 and 6, and very rarely cyl 1 and 4.
To overcome this very annoying problem, I tried these:
- All spark plugs have been replaced, ignition coils replaced, nothing changed.
- All injectors sent to Bosch center, cleaned and tested, reinstalled, nothing changed. If I change the position of the injectors and recode them for new locations, still the same old cylinders misfire. Nothing moves with injectors.
- I opened up the engine wiring harness top section, checked and rewired all injector/ignition coil wires, common +12V and ground points. Nothing changed.
- Cold compression test done. All cylinders are around 215-220psi and above, very very good. No problems seen.
- All 8 cylinder tops and combustion chamber checked with flex camera, cyl 8 has more carbon deposits on the piston than the remaining 7 but nothing seems severe. I removed the complete intake manifold, cyl 8 intake port seem more CLEANER than the other 7 but all of them shows heavy carbon deposit, more or less. SO I decided to clean the intake ports and valves. With brake cleaner and thinner, I removed all carbon deposits from the ports and valve bodies. Problem is still there.
- I replaced all 4 knock sensors, nothing changed. If I drive the car with knock sensors unplugged, the problem is 90% goes away but performance goes significantly low, naturally.
- I test drove the car with Xentry connected, low/high fuel pressures, intake and boost pressures, engine temp, 4 camshaft angles etc all values are in the range. When I increase the load and start the shake/misfire, I see cyl 8 and cyl 7 misfire counters goes up like crazy and eventually engine computer shuts off cyl 8 and sometimes 7 too.
- Finally I tried STP intake valve cleaner fluid to clean the possible remaining carbon deposits (an experienced MB mechanic told me M278 engines are very sensitive to intake valve carbon deposit), no help.
I have ZERO performance issues, car literally flies if you push hard on high rpm's, no smoke, no hesitation. Throttle response is very very good. If you go over 2,200 rpm and floor it, car is like a rocket.
Under this circumstance, I think the engine is good mechanically. I am considering to change the engine wiring harness thinking about my past experience on my ex Ferrari 599GTB, showing 'transmission failure - hydraulic pump pressure low" error and putting car to neutral which makes car non-driveable for 5-10 mins and comes back to normal until next occurrence in maybe 1-2 months. I saw many similar 'mystic' problems caused by wiring harnesses.
Last note: I drove a 2013 GL550 some years ago, that one was showing similar cold start misfire thing but I discovered a service bulletin about it, reprogrammed the engine computer and problem solved forever. This time, there is no such solution
Any other experiences/comments on this mystery?
12-18-2022, 02:53 AM
#2
Surely, you must have more than one diagnostic trouble code. What are they? The mass air flow sensor is a common cause of your trouble.
You replaced spark plugs. Did you remember to replace the rubber spark plug boots as well?
Given all you have done, the problem still sounds mechanical. I suspect a sticking valve. The heavy carbon deposits are a serious red flag, and so is the shake at cold start. Carbon can work its way past the valve stem seals, caking high up on the valve stems, causing them to rub the valve guides and thus obstruct movement. Carbon also very commonly builds on the valve seats in the heads and can be difficult to remove. Temporary valve binding is most likely when the engine is cold, and at low rpm when warm, but disappears at high rpm. This phenomenon occurs more frequently on turbo engines and high compression engines, both of which you have, due to accelerated carbon build-up during warm-up and local driving. Even though you have cleaned the parts of the values you can see when removing the intake manifold, the areas I'm describing cannot be seen unless you completely remove the valves from the heads.
If the car is still under warranty, have the affected cylinder head replaced (that was the solution in another forum post). If not, start by flushing the crankcase with this for 30 minutes at idle (not just 5 minutes, as the directions say). Follow-up with one quart in the crankcase for 3-5k miles (changing the oil every 1k miles). Also, that can of STP in the gas tank just won't cut it. Use a 10x amount of in the gas tank, combined with 5x Marvel Mystery Oil in the gas tank, combined with 2 cans of . Run until empty. After that, continue to use 5x amount of Star Tron and 1x concentration of MMO indefinitely in the gas. I experienced other carbon related problems in my '08 E350 for years until I began using these products. I also now use Red Line oil and and my sticky valves and poor acceleration problems are gone for good.
You replaced spark plugs. Did you remember to replace the rubber spark plug boots as well?
Given all you have done, the problem still sounds mechanical. I suspect a sticking valve. The heavy carbon deposits are a serious red flag, and so is the shake at cold start. Carbon can work its way past the valve stem seals, caking high up on the valve stems, causing them to rub the valve guides and thus obstruct movement. Carbon also very commonly builds on the valve seats in the heads and can be difficult to remove. Temporary valve binding is most likely when the engine is cold, and at low rpm when warm, but disappears at high rpm. This phenomenon occurs more frequently on turbo engines and high compression engines, both of which you have, due to accelerated carbon build-up during warm-up and local driving. Even though you have cleaned the parts of the values you can see when removing the intake manifold, the areas I'm describing cannot be seen unless you completely remove the valves from the heads.
If the car is still under warranty, have the affected cylinder head replaced (that was the solution in another forum post). If not, start by flushing the crankcase with this for 30 minutes at idle (not just 5 minutes, as the directions say). Follow-up with one quart in the crankcase for 3-5k miles (changing the oil every 1k miles). Also, that can of STP in the gas tank just won't cut it. Use a 10x amount of in the gas tank, combined with 5x Marvel Mystery Oil in the gas tank, combined with 2 cans of . Run until empty. After that, continue to use 5x amount of Star Tron and 1x concentration of MMO indefinitely in the gas. I experienced other carbon related problems in my '08 E350 for years until I began using these products. I also now use Red Line oil and and my sticky valves and poor acceleration problems are gone for good.
12-18-2022, 08:47 AM
#3
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Dear Forum Members,
I used to read MB World forums for years but this is the first time that I feel hopeless and need help...
I have a 2018 GLS550 and around 20k miles, a very weird misfiring problem started. This is what happens:
- Sometimes (30-40% of cold starts), engine starts with immediate misfiring at cyl 8 after cranking, check engine light blinks and stays on, turning off/on does not help, after driving for 2-3 mins and engine gets a bit warm then I turn off/on the engine, everything turns back to normal, car runs perfectly smooth with all cylinders on, no performance issues. Even sometimes, check engine light goes off too!
- The main problem is the misfiring when driving. A very hard shaking starts if I drive at high gears (6-7-8-9) with high load (more than 50% of throttle) and engine rpm between 1,800-2,200 rpm. Under these conditions, an immediate shaking starts (not everytime but 60-70% occurrence), check engine light starts blinking and stays on, engine control unit shuts off the misfiring cylinder and everything comes back to perfectly normal if I turn the key off/on and restart the engine. When I check the fault codes, I see 100% cylinder 8 misfire and 75-80% of the times cyl 7 and 6, and very rarely cyl 1 and 4.
To overcome this very annoying problem, I tried these:
- All spark plugs have been replaced, ignition coils replaced, nothing changed.
- All injectors sent to Bosch center, cleaned and tested, reinstalled, nothing changed. If I change the position of the injectors and recode them for new locations, still the same old cylinders misfire. Nothing moves with injectors.
- I opened up the engine wiring harness top section, checked and rewired all injector/ignition coil wires, common +12V and ground points. Nothing changed.
- Cold compression test done. All cylinders are around 215-220psi and above, very very good. No problems seen.
- All 8 cylinder tops and combustion chamber checked with flex camera, cyl 8 has more carbon deposits on the piston than the remaining 7 but nothing seems severe. I removed the complete intake manifold, cyl 8 intake port seem more CLEANER than the other 7 but all of them shows heavy carbon deposit, more or less. SO I decided to clean the intake ports and valves. With brake cleaner and thinner, I removed all carbon deposits from the ports and valve bodies. Problem is still there.
- I replaced all 4 knock sensors, nothing changed. If I drive the car with knock sensors unplugged, the problem is 90% goes away but performance goes significantly low, naturally.
- I test drove the car with Xentry connected, low/high fuel pressures, intake and boost pressures, engine temp, 4 camshaft angles etc all values are in the range. When I increase the load and start the shake/misfire, I see cyl 8 and cyl 7 misfire counters goes up like crazy and eventually engine computer shuts off cyl 8 and sometimes 7 too.
- Finally I tried STP intake valve cleaner fluid to clean the possible remaining carbon deposits (an experienced MB mechanic told me M278 engines are very sensitive to intake valve carbon deposit), no help.
I have ZERO performance issues, car literally flies if you push hard on high rpm's, no smoke, no hesitation. Throttle response is very very good. If you go over 2,200 rpm and floor it, car is like a rocket.
Under this circumstance, I think the engine is good mechanically. I am considering to change the engine wiring harness thinking about my past experience on my ex Ferrari 599GTB, showing 'transmission failure - hydraulic pump pressure low" error and putting car to neutral which makes car non-driveable for 5-10 mins and comes back to normal until next occurrence in maybe 1-2 months. I saw many similar 'mystic' problems caused by wiring harnesses.
Last note: I drove a 2013 GL550 some years ago, that one was showing similar cold start misfire thing but I discovered a service bulletin about it, reprogrammed the engine computer and problem solved forever. This time, there is no such solution
Any other experiences/comments on this mystery?
I used to read MB World forums for years but this is the first time that I feel hopeless and need help...
I have a 2018 GLS550 and around 20k miles, a very weird misfiring problem started. This is what happens:
- Sometimes (30-40% of cold starts), engine starts with immediate misfiring at cyl 8 after cranking, check engine light blinks and stays on, turning off/on does not help, after driving for 2-3 mins and engine gets a bit warm then I turn off/on the engine, everything turns back to normal, car runs perfectly smooth with all cylinders on, no performance issues. Even sometimes, check engine light goes off too!
- The main problem is the misfiring when driving. A very hard shaking starts if I drive at high gears (6-7-8-9) with high load (more than 50% of throttle) and engine rpm between 1,800-2,200 rpm. Under these conditions, an immediate shaking starts (not everytime but 60-70% occurrence), check engine light starts blinking and stays on, engine control unit shuts off the misfiring cylinder and everything comes back to perfectly normal if I turn the key off/on and restart the engine. When I check the fault codes, I see 100% cylinder 8 misfire and 75-80% of the times cyl 7 and 6, and very rarely cyl 1 and 4.
To overcome this very annoying problem, I tried these:
- All spark plugs have been replaced, ignition coils replaced, nothing changed.
- All injectors sent to Bosch center, cleaned and tested, reinstalled, nothing changed. If I change the position of the injectors and recode them for new locations, still the same old cylinders misfire. Nothing moves with injectors.
- I opened up the engine wiring harness top section, checked and rewired all injector/ignition coil wires, common +12V and ground points. Nothing changed.
- Cold compression test done. All cylinders are around 215-220psi and above, very very good. No problems seen.
- All 8 cylinder tops and combustion chamber checked with flex camera, cyl 8 has more carbon deposits on the piston than the remaining 7 but nothing seems severe. I removed the complete intake manifold, cyl 8 intake port seem more CLEANER than the other 7 but all of them shows heavy carbon deposit, more or less. SO I decided to clean the intake ports and valves. With brake cleaner and thinner, I removed all carbon deposits from the ports and valve bodies. Problem is still there.
- I replaced all 4 knock sensors, nothing changed. If I drive the car with knock sensors unplugged, the problem is 90% goes away but performance goes significantly low, naturally.
- I test drove the car with Xentry connected, low/high fuel pressures, intake and boost pressures, engine temp, 4 camshaft angles etc all values are in the range. When I increase the load and start the shake/misfire, I see cyl 8 and cyl 7 misfire counters goes up like crazy and eventually engine computer shuts off cyl 8 and sometimes 7 too.
- Finally I tried STP intake valve cleaner fluid to clean the possible remaining carbon deposits (an experienced MB mechanic told me M278 engines are very sensitive to intake valve carbon deposit), no help.
I have ZERO performance issues, car literally flies if you push hard on high rpm's, no smoke, no hesitation. Throttle response is very very good. If you go over 2,200 rpm and floor it, car is like a rocket.
Under this circumstance, I think the engine is good mechanically. I am considering to change the engine wiring harness thinking about my past experience on my ex Ferrari 599GTB, showing 'transmission failure - hydraulic pump pressure low" error and putting car to neutral which makes car non-driveable for 5-10 mins and comes back to normal until next occurrence in maybe 1-2 months. I saw many similar 'mystic' problems caused by wiring harnesses.
Last note: I drove a 2013 GL550 some years ago, that one was showing similar cold start misfire thing but I discovered a service bulletin about it, reprogrammed the engine computer and problem solved forever. This time, there is no such solution
Any other experiences/comments on this mystery?
What modifications are on this vehicle? What is your ownership history?
- More carbon on #8 piston crown is consistent with misfire. This confirms misfire (it helps sometimes to state the obvious).
- Did you see scoring on the cylinder walls with the camera?
- Did you do a leakdown compression test?
- Did you inspect for oil in the wiring connectors for the cam position sensors and cam magnets?
12-18-2022, 12:28 PM
#4
Impressive diagnosis, well done. Are you a service tech and do you have a lift at your disposal?
What modifications are on this vehicle? What is your ownership history?
- More carbon on #8 piston crown is consistent with misfire. This confirms misfire (it helps sometimes to state the obvious).
- Did you see scoring on the cylinder walls with the camera?
- Did you do a leakdown compression test?
- Did you inspect for oil in the wiring connectors for the cam position sensors and cam magnets?
What modifications are on this vehicle? What is your ownership history?
- More carbon on #8 piston crown is consistent with misfire. This confirms misfire (it helps sometimes to state the obvious).
- Did you see scoring on the cylinder walls with the camera?
- Did you do a leakdown compression test?
- Did you inspect for oil in the wiring connectors for the cam position sensors and cam magnets?
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chassis (12-18-2022)
12-19-2022, 10:47 AM
#5
Junior Member
Thread Starter
Surely, you must have more than one diagnostic trouble code. What are they? The mass air flow sensor is a common cause of your trouble.
You replaced spark plugs. Did you remember to replace the rubber spark plug boots as well?
Given all you have done, the problem still sounds mechanical. I suspect a sticking valve. The heavy carbon deposits are a serious red flag, and so is the shake at cold start. Carbon can work its way past the valve stem seals, caking high up on the valve stems, causing them to rub the valve guides and thus obstruct movement. Carbon also very commonly builds on the valve seats in the heads and can be difficult to remove. Temporary valve binding is most likely when the engine is cold, and at low rpm when warm, but disappears at high rpm. This phenomenon occurs more frequently on turbo engines and high compression engines, both of which you have, due to accelerated carbon build-up during warm-up and local driving. Even though you have cleaned the parts of the values you can see when removing the intake manifold, the areas I'm describing cannot be seen unless you completely remove the valves from the heads.
If the car is still under warranty, have the affected cylinder head replaced (that was the solution in another forum post). If not, start by flushing the crankcase with this synthetic motor flush for 30 minutes at idle (not just 5 minutes, as the directions say). Follow-up with one quart Marvel Mystery Oil in the crankcase for 3-5k miles (changing the oil every 1k miles). Also, that can of STP in the gas tank just won't cut it. Use a 10x amount of Star Tron in the gas tank, combined with 5x Marvel Mystery Oil in the gas tank, combined with 2 cans of BG44K. Run until empty. After that, continue to use 5x amount of Star Tron and 1x concentration of MMO indefinitely in the gas. I experienced other carbon related problems in my '08 E350 for years until I began using these products. I also now use Red Line oil and Archoil 9100 and my sticky valves and poor acceleration problems are gone for good.
You replaced spark plugs. Did you remember to replace the rubber spark plug boots as well?
Given all you have done, the problem still sounds mechanical. I suspect a sticking valve. The heavy carbon deposits are a serious red flag, and so is the shake at cold start. Carbon can work its way past the valve stem seals, caking high up on the valve stems, causing them to rub the valve guides and thus obstruct movement. Carbon also very commonly builds on the valve seats in the heads and can be difficult to remove. Temporary valve binding is most likely when the engine is cold, and at low rpm when warm, but disappears at high rpm. This phenomenon occurs more frequently on turbo engines and high compression engines, both of which you have, due to accelerated carbon build-up during warm-up and local driving. Even though you have cleaned the parts of the values you can see when removing the intake manifold, the areas I'm describing cannot be seen unless you completely remove the valves from the heads.
If the car is still under warranty, have the affected cylinder head replaced (that was the solution in another forum post). If not, start by flushing the crankcase with this synthetic motor flush for 30 minutes at idle (not just 5 minutes, as the directions say). Follow-up with one quart Marvel Mystery Oil in the crankcase for 3-5k miles (changing the oil every 1k miles). Also, that can of STP in the gas tank just won't cut it. Use a 10x amount of Star Tron in the gas tank, combined with 5x Marvel Mystery Oil in the gas tank, combined with 2 cans of BG44K. Run until empty. After that, continue to use 5x amount of Star Tron and 1x concentration of MMO indefinitely in the gas. I experienced other carbon related problems in my '08 E350 for years until I began using these products. I also now use Red Line oil and Archoil 9100 and my sticky valves and poor acceleration problems are gone for good.
Thank you for your reply and comments. Regarding the spark plug boots, I have replaced all 8 ignition coils together with the boots so I assume I am safe on that side. For the DTC, yes I have P0308 every time together with P0307 most of the time and very rarely P0304.. I assume, my main problem is P0308 and when I push the engine to create the rattle (high gear-high load-low rpm combination), the shake is so strong sometimes and knock sensors detect cyl 8 and 7 misfiring together bc there is one knock sensor sitting in between cyl 8 and 7 and sound waves refer on both cylinders. And cyl 4 is sitting on the opposite side so that knock sensor may be affected too.
On the other hand, 'sticky valve' thing sounds very interesting to me, never had such a problem before. If one or both of the intake valves delay in closing, this will cause misfire for sure plus the high pressure combustion chamber mixture/gases leak back to the intake causing the following:
- Less carbon deposit on cyl 8 intake due to reverse washing (yes I saw cyl 8 intake is very clean in terms of carbon deposit, remaining 7 intakes were dirty as hell)
- unwanted HC in intake possibly effecting other cylinders' mixture (when I follow up lambda sensor values, I see the engine ECU is pushing the engine more on the lean side, also engine is heating up -not overheating but I see the temp gauge reaches to normal range in even 1-2 miles!- very quick due to lean mixture, sticky valves may be the cause of this).
- When I press the throttle and create intake boost, then lift off immediately, I hear the pressure release noise at the intake line is not smooth like 'pufffffff' in one shot but like 'puffff-pufff-puff-puf' along with a very little shake with the body. Can all of these caused by the intake valve leak back to intake manifold?
Maybe better to insert a manometer to brake booster line and watch the pressure change in the intake chamber?
-
12-19-2022, 10:54 AM
#6
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You need a XENTRY system or access to one.
Last edited by chassis; 12-19-2022 at 11:40 AM.
12-19-2022, 10:59 AM
#7
Junior Member
Thread Starter
Thank you very much Chassis, I am not a service tech but a mechanical engineer with 20 years of professional experience at OEM level, now running my own business in Miami. I have 25k sqft facility for car personalization (not for mechanical repairs but I do if I need it for my own cars and for friends sometimes). I bought this GLS550 from NYC last year and it was a flood salvage with a very little internal damage, I have replaced the modules sitting at the bottom of the interior cabin and all came back to life but this engine problem. This car has always been taken care of MB dealer in NJ, I checked the full history of the car but there is no such a complaint in the past. Maybe the water infiltration into crankcase seized the valve lifter or the valves which cause the stickiness? What do you think? (Yes, the engine oil was bad when I got the car and have been flushed/replaced 3 times before I start driving it).
Regarding your questions, all the cylinder bores look clean including cyl 8, no scoring.. Leakdown compression test not done and I see very little oil in cam position sensors -I read that it is a common problem- I consider to replace them all but I am not sure they would cause my problem. Do they?
Regarding your questions, all the cylinder bores look clean including cyl 8, no scoring.. Leakdown compression test not done and I see very little oil in cam position sensors -I read that it is a common problem- I consider to replace them all but I am not sure they would cause my problem. Do they?
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12-19-2022, 11:01 AM
#8
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chassis (12-19-2022)
12-19-2022, 11:02 AM
#9
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Thread Starter
That also sound very interesting to me. Let me repeat the cold compression test and share a sample video here so we all comment on that better. Thank you!
12-19-2022, 11:44 AM
#10
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Thank you very much Chassis, I am not a service tech but a mechanical engineer with 20 years of professional experience at OEM level, now running my own business in Miami. I have 25k sqft facility for car personalization (not for mechanical repairs but I do if I need it for my own cars and for friends sometimes). I bought this GLS550 from NYC last year and it was a flood salvage with a very little internal damage, I have replaced the modules sitting at the bottom of the interior cabin and all came back to life but this engine problem. This car has always been taken care of MB dealer in NJ, I checked the full history of the car but there is no such a complaint in the past. Maybe the water infiltration into crankcase seized the valve lifter or the valves which cause the stickiness? What do you think? (Yes, the engine oil was bad when I got the car and have been flushed/replaced 3 times before I start driving it).
Regarding your questions, all the cylinder bores look clean including cyl 8, no scoring.. Leakdown compression test not done and I see very little oil in cam position sensors -I read that it is a common problem- I consider to replace them all but I am not sure they would cause my problem. Do they?
Regarding your questions, all the cylinder bores look clean including cyl 8, no scoring.. Leakdown compression test not done and I see very little oil in cam position sensors -I read that it is a common problem- I consider to replace them all but I am not sure they would cause my problem. Do they?
I would abandon the mechanical diagnosis for now and bring yourself to full satisfaction that all modules are 100% functional, using XENTRY diagnosis. I can see a week of intensive XENTRY sessions to accomplish this.
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SSB3435 (02-13-2023)
12-19-2022, 01:36 PM
#11
Junior Member
Thread Starter
Flood salvage is material information that would have been helpful to disclose in the original post. Need to take an “anything could be possible” approach with this, given the salvage status.
I would abandon the mechanical diagnosis for now and bring yourself to full satisfaction that all modules are 100% functional, using XENTRY diagnosis. I can see a week of intensive XENTRY sessions to accomplish this.
I would abandon the mechanical diagnosis for now and bring yourself to full satisfaction that all modules are 100% functional, using XENTRY diagnosis. I can see a week of intensive XENTRY sessions to accomplish this.
12-19-2022, 01:40 PM
#12
Junior Member
Thread Starter
These are cylinder 8 cold compression tests. Surprisingly, the max value seems below 180psi. It was 215-220 6 months (and approx 500 miles) ago.
12-19-2022, 01:46 PM
#14
Junior Member
Thread Starter
And these are the cyl 8 spark plug (on the left) and cyl 5 spark plug (on the right). The yellow ring/stain at the bottom catches my attention. Is it a sign of working at higher temperatures at cyl 8? Btw, this was a brand new set installed 500 miles ago and original MB part.
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chassis (12-19-2022)
12-19-2022, 10:20 PM
#15
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And these are the cyl 8 spark plug (on the left) and cyl 5 spark plug (on the right). The yellow ring/stain at the bottom catches my attention. Is it a sign of working at higher temperatures at cyl 8? Btw, this was a brand new set installed 500 miles ago and original MB part.
Low compression and suspect spark plug points to something not right with #8.
Starting to seem like sticky valve guide. https://mbworld.org/forums/cls-coupe...sb-notice.html
Rebuild from the resident M278 expert @arsupisemnet https://mbworld.org/forums/gl-class-...8-rebuild.html
Last edited by chassis; 12-19-2022 at 10:28 PM.
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SSB3435 (02-13-2023)
12-20-2022, 12:20 AM
#16
Hi TechSurfer,
Thank you for your reply and comments. Regarding the spark plug boots, I have replaced all 8 ignition coils together with the boots so I assume I am safe on that side. For the DTC, yes I have P0308 every time together with P0307 most of the time and very rarely P0304.. I assume, my main problem is P0308 and when I push the engine to create the rattle (high gear-high load-low rpm combination), the shake is so strong sometimes and knock sensors detect cyl 8 and 7 misfiring together bc there is one knock sensor sitting in between cyl 8 and 7 and sound waves refer on both cylinders. And cyl 4 is sitting on the opposite side so that knock sensor may be affected too.
On the other hand, 'sticky valve' thing sounds very interesting to me, never had such a problem before. If one or both of the intake valves delay in closing, this will cause misfire for sure plus the high pressure combustion chamber mixture/gases leak back to the intake causing the following:
- Less carbon deposit on cyl 8 intake due to reverse washing (yes I saw cyl 8 intake is very clean in terms of carbon deposit, remaining 7 intakes were dirty as hell)
- unwanted HC in intake possibly effecting other cylinders' mixture (when I follow up lambda sensor values, I see the engine ECU is pushing the engine more on the lean side, also engine is heating up -not overheating but I see the temp gauge reaches to normal range in even 1-2 miles!- very quick due to lean mixture, sticky valves may be the cause of this).
- When I press the throttle and create intake boost, then lift off immediately, I hear the pressure release noise at the intake line is not smooth like 'pufffffff' in one shot but like 'puffff-pufff-puff-puf' along with a very little shake with the body. Can all of these caused by the intake valve leak back to intake manifold?
Maybe better to insert a manometer to brake booster line and watch the pressure change in the intake chamber?
-
Thank you for your reply and comments. Regarding the spark plug boots, I have replaced all 8 ignition coils together with the boots so I assume I am safe on that side. For the DTC, yes I have P0308 every time together with P0307 most of the time and very rarely P0304.. I assume, my main problem is P0308 and when I push the engine to create the rattle (high gear-high load-low rpm combination), the shake is so strong sometimes and knock sensors detect cyl 8 and 7 misfiring together bc there is one knock sensor sitting in between cyl 8 and 7 and sound waves refer on both cylinders. And cyl 4 is sitting on the opposite side so that knock sensor may be affected too.
On the other hand, 'sticky valve' thing sounds very interesting to me, never had such a problem before. If one or both of the intake valves delay in closing, this will cause misfire for sure plus the high pressure combustion chamber mixture/gases leak back to the intake causing the following:
- Less carbon deposit on cyl 8 intake due to reverse washing (yes I saw cyl 8 intake is very clean in terms of carbon deposit, remaining 7 intakes were dirty as hell)
- unwanted HC in intake possibly effecting other cylinders' mixture (when I follow up lambda sensor values, I see the engine ECU is pushing the engine more on the lean side, also engine is heating up -not overheating but I see the temp gauge reaches to normal range in even 1-2 miles!- very quick due to lean mixture, sticky valves may be the cause of this).
- When I press the throttle and create intake boost, then lift off immediately, I hear the pressure release noise at the intake line is not smooth like 'pufffffff' in one shot but like 'puffff-pufff-puff-puf' along with a very little shake with the body. Can all of these caused by the intake valve leak back to intake manifold?
Maybe better to insert a manometer to brake booster line and watch the pressure change in the intake chamber?
-
Lots of Marvel Mystery Oil in the crankcase and fuel could, under ordinary conditions, solve the problem. I have read the rest of your posts, however, and see your crankcase has been subject to water inundation. Since I have owned boats in the past that sank, subjecting an engine to water, I know that the resultant corrosion can be devastating. I fear you have serious damage, especially now that cylinder #8 is below 20% compression compared to the other cylinders.
Last edited by TechSurfer; 12-20-2022 at 01:41 AM.
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SSB3435 (02-13-2023)
01-06-2023, 03:14 PM
#17
Junior Member
Thread Starter
Surely, you must have more than one diagnostic trouble code. What are they? The mass air flow sensor is a common cause of your trouble.
You replaced spark plugs. Did you remember to replace the rubber spark plug boots as well?
Given all you have done, the problem still sounds mechanical. I suspect a sticking valve. The heavy carbon deposits are a serious red flag, and so is the shake at cold start. Carbon can work its way past the valve stem seals, caking high up on the valve stems, causing them to rub the valve guides and thus obstruct movement. Carbon also very commonly builds on the valve seats in the heads and can be difficult to remove. Temporary valve binding is most likely when the engine is cold, and at low rpm when warm, but disappears at high rpm. This phenomenon occurs more frequently on turbo engines and high compression engines, both of which you have, due to accelerated carbon build-up during warm-up and local driving. Even though you have cleaned the parts of the values you can see when removing the intake manifold, the areas I'm describing cannot be seen unless you completely remove the valves from the heads.
If the car is still under warranty, have the affected cylinder head replaced (that was the solution in another forum post). If not, start by flushing the crankcase with this synthetic motor flush for 30 minutes at idle (not just 5 minutes, as the directions say). Follow-up with one quart Marvel Mystery Oil in the crankcase for 3-5k miles (changing the oil every 1k miles). Also, that can of STP in the gas tank just won't cut it. Use a 10x amount of Star Tron in the gas tank, combined with 5x Marvel Mystery Oil in the gas tank, combined with 2 cans of BG44K. Run until empty. After that, continue to use 5x amount of Star Tron and 1x concentration of MMO indefinitely in the gas. I experienced other carbon related problems in my '08 E350 for years until I began using these products. I also now use Red Line oil and Archoil 9100 and my sticky valves and poor acceleration problems are gone for good.
You replaced spark plugs. Did you remember to replace the rubber spark plug boots as well?
Given all you have done, the problem still sounds mechanical. I suspect a sticking valve. The heavy carbon deposits are a serious red flag, and so is the shake at cold start. Carbon can work its way past the valve stem seals, caking high up on the valve stems, causing them to rub the valve guides and thus obstruct movement. Carbon also very commonly builds on the valve seats in the heads and can be difficult to remove. Temporary valve binding is most likely when the engine is cold, and at low rpm when warm, but disappears at high rpm. This phenomenon occurs more frequently on turbo engines and high compression engines, both of which you have, due to accelerated carbon build-up during warm-up and local driving. Even though you have cleaned the parts of the values you can see when removing the intake manifold, the areas I'm describing cannot be seen unless you completely remove the valves from the heads.
If the car is still under warranty, have the affected cylinder head replaced (that was the solution in another forum post). If not, start by flushing the crankcase with this synthetic motor flush for 30 minutes at idle (not just 5 minutes, as the directions say). Follow-up with one quart Marvel Mystery Oil in the crankcase for 3-5k miles (changing the oil every 1k miles). Also, that can of STP in the gas tank just won't cut it. Use a 10x amount of Star Tron in the gas tank, combined with 5x Marvel Mystery Oil in the gas tank, combined with 2 cans of BG44K. Run until empty. After that, continue to use 5x amount of Star Tron and 1x concentration of MMO indefinitely in the gas. I experienced other carbon related problems in my '08 E350 for years until I began using these products. I also now use Red Line oil and Archoil 9100 and my sticky valves and poor acceleration problems are gone for good.
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SSB3435 (01-06-2023)
01-07-2023, 01:18 AM
#19
You are the first person who's actually followed my advice in a forum over the past few years. I usually just get a lot of angry, silly comments from people who have not done a shred of research or who have never actually used the products.
Last edited by TechSurfer; 01-07-2023 at 01:24 AM.
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SSB3435 (01-07-2023)
01-09-2023, 12:20 PM
#20
Junior Member
Thread Starter
Please do send me updates, I'm following this thread. I am very curious to see your results. I just used them all in my E350 with an oil change over the Christmas holidays and the results are amazing. Car runs like showroom new and gets 31 mpg on the highway, which is much higher than the 24 mpg I used to get before all these additives and even the theoretical 26.5 the EPA promised.
You are the first person who's actually followed my advice in a forum over the past few years. I usually just get a lot of angry, silly comments from people who have not done a shred of research or who have never actually used the products.
You are the first person who's actually followed my advice in a forum over the past few years. I usually just get a lot of angry, silly comments from people who have not done a shred of research or who have never actually used the products.
So far the results are: All cold starts in the morning are good, no rough idle or dead cyl#8 observed. Car starts and runs very very nice. But, the other symptom is still there, I can repeat the problem under high load-low rpm (1,600-2,000 range only) conditions at high gears. Changing the driving mode to SPORT decrease the problem a bit since everytime I want to accelerate, it downshift and pushes the engine to higher rpm's where I have zero problems. But in COMFORT mode, if the rpm needle falls in between 1,600-2,000 range and I push the throttle without downshifting, everytime engine starts to shake with increasing turbo boost and CEL comes on, cyl#8 shuts down immediately due to extreme misfiring, then I stop the car, turn off and on the ignition, everything comes back to life as if nothing happened... Have no idea if I will ever get rid of this problem without opening the 5-8 cylinder head
01-09-2023, 12:27 PM
#22
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SSB3435 (02-13-2023)
01-09-2023, 12:28 PM
#23
Out Of Control!!
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SSB3435 (02-13-2023)
01-09-2023, 10:03 PM
#24
The engine flush done... Filled with the new oil and additives.. Mystery oil is now flowing in the veins of M278. Fuel tank filled with 93 octane premium fuel, advised quantities of mystery oil and fuel treatment additives included... So far I drove it approx 200 miles, I feel better throttle response and slightly better mpg (16,9 vs 15.8 but this may be due to temperature change since FL is a bit cold nowadays, 64F in the mornings and 75F in the daytime vs usual 80-85F range).
So far the results are: All cold starts in the morning are good, no rough idle or dead cyl#8 observed. Car starts and runs very very nice. But, the other symptom is still there, I can repeat the problem under high load-low rpm (1,600-2,000 range only) conditions at high gears. Changing the driving mode to SPORT decrease the problem a bit since everytime I want to accelerate, it downshift and pushes the engine to higher rpm's where I have zero problems. But in COMFORT mode, if the rpm needle falls in between 1,600-2,000 range and I push the throttle without downshifting, everytime engine starts to shake with increasing turbo boost and CEL comes on, cyl#8 shuts down immediately due to extreme misfiring, then I stop the car, turn off and on the ignition, everything comes back to life as if nothing happened... Have no idea if I will ever get rid of this problem without opening the 5-8 cylinder head
So far the results are: All cold starts in the morning are good, no rough idle or dead cyl#8 observed. Car starts and runs very very nice. But, the other symptom is still there, I can repeat the problem under high load-low rpm (1,600-2,000 range only) conditions at high gears. Changing the driving mode to SPORT decrease the problem a bit since everytime I want to accelerate, it downshift and pushes the engine to higher rpm's where I have zero problems. But in COMFORT mode, if the rpm needle falls in between 1,600-2,000 range and I push the throttle without downshifting, everytime engine starts to shake with increasing turbo boost and CEL comes on, cyl#8 shuts down immediately due to extreme misfiring, then I stop the car, turn off and on the ignition, everything comes back to life as if nothing happened... Have no idea if I will ever get rid of this problem without opening the 5-8 cylinder head
You want to avoid the misfire because you risk burning the valve, which will obviously be permanent damage.
Last edited by TechSurfer; 01-09-2023 at 10:46 PM. Reason: missed something
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SSB3435 (02-13-2023)
01-09-2023, 10:31 PM
#25
You can speed the MMO process along by keeping the engine at higher rpm, so don't use Comfort mode for now. Also, raising the idle to about 2k rpm in neutral (at stop lights, etc.) for a minute or two enhances the cleaning power due to higher temps.
Last edited by TechSurfer; 01-09-2023 at 10:34 PM.
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SSB3435 (02-13-2023)
