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So I am having an issue with my 2017 GLE 350. I am getting a cylinder 2 misfire error code. I replaced the spark plug in cylinder 2 (the middle cylinder on the passenger side) and swapped the coil from cylinder 1 with it. My thought was that if the problem went away I could assume it was a bad plug. If the misfire issue switched to cylinder 1 then I could assume it was the coil.
Surprisingly, when I put it all back together and cleared the codes the misfire error came back again on cylinder 2.
Any suggestions on what else I should be looking for?
When the engine is running at idle, if I give it a little throttle it does sound like maybe some air is leaking (or maybe just the sound caused by a misfire)?
I have read a vacuum leak could be to blame - but not sure what/where I would look for that. Any thoughts or assistance would be greatly appreciated!
So I am having an issue with my 2017 GLE 350. I am getting a cylinder 2 misfire error code. I replaced the spark plug in cylinder 2 (the middle cylinder on the passenger side) and swapped the coil from cylinder 1 with it. My thought was that if the problem went away I could assume it was a bad plug. If the misfire issue switched to cylinder 1 then I could assume it was the coil.
Surprisingly, when I put it all back together and cleared the codes the misfire error came back again on cylinder 2.
Any suggestions on what else I should be looking for?
When the engine is running at idle, if I give it a little throttle it does sound like maybe some air is leaking (or maybe just the sound caused by a misfire)?
I have read a vacuum leak could be to blame - but not sure what/where I would look for that. Any thoughts or assistance would be greatly appreciated!
How many miles on it?
How long have you owned it?
What modifications are on the car?
What led to the first indication of a problem?
What is the service history of this vehicle?
The symptoms you are describing are unusual for this model if it has been fully maintained and unmodified.
Vehicle has 73000 miles
I have owned it for 2 years (almost to the date)
No modifications made
First indications were check engine light with rough running engine - scans consistently show Cylinder 2 misfire - seemed to run fine prior
Service history prior to this? - purchased from Mercedes Dealer - history showed leased vehicle with maint performed at regular intervals
Vehicle is in Minnesota. Temps just recently started dipping below freezing for the year. Stored in heated garage when not in use. Wife drive to the grocery store - ran fine on the way to the store. Came out of the store and check engine came on upon starting along with rough running.
I also was able to perform a compression test via Xentry, results attached:
I also performed a fuel injector test, in which each injector was turned off one by one. When I turned off cylinders 1, 3, 4, 5, or 6 - the engine slowed down and ran rougher. When I turned off cylinder #2 there was no change. This leads me to suspect injector 2 is faulty? I see no other reason why swapping the plug and coil would have no effect.
Last edited by ccrobin; Dec 1, 2022 at 04:54 PM.
Reason: Supplemental info
Good job on the XENTRY test, this will lead you to the solution.
Coil "wires" can be problematic, but it is uncommon. The connector may not be fully seated and latched.
I would spend more time with the injector test in XENTRY. If you are convinced the problem isn't spark plug, coil or wiring related, a potential next step is to swap injectors and see if the problem follows the injector.
Persistent misfire without an obvious cause is uncommon with this engine.
They don't seem to snap onto the plugs, it seems more like they just slide on and touch. Am I wrong on that? Should they actually snap on like a traditional spark plug wire would?
The design of the plug does not look like one that snaps into the wire socket, so just wondering if the chances were a bad plug and I just didn't get the swapped coil seated correctly on the same cylinder?
Also, am I correct in thinking that Cylinder #2 is the middle cylinder on the passenger side (US)? If not, then I likely did not change the correct plug and coil.
Yes, there are two affirmative snaps for the coil connector. Latching means push the connector all the way onto the coil until it clicks, then lock the security latch.
Sounds like the coil connector might not be fully seated and latched.
Yes, there are two affirmative snaps for the coil connector. Latching means push the connector all the way onto the coil until it clicks, then lock the security latch.
Sounds like the coil connector might not be fully seated and latched.
There is no security latch on mine. It just pushes on and then 2 screws attach the coil.
It might be the photo, but it looks like the grey latches are not fully latched. This may or may not cause misfire, but to rule out bad coil connection the connector needs to be fully seated and latched.
Are you completely clear on how the connector and latches operate? They are tricky when first learning them.
It might be the photo, but it looks like the grey latches are not fully latched. This may or may not cause misfire, but to rule out bad coil connection the connector needs to be fully seated and latched.
Are you completely clear on how the connector and latches operate? They are tricky when first learning them.
I see what you mean by latched now. I’ll check that in the AM and report back. Thanks a ton for your comments to assist!
So I am having an issue with my 2017 GLE 350. I am getting a cylinder 2 misfire error code. I replaced the spark plug in cylinder 2 (the middle cylinder on the passenger side) and swapped the coil from cylinder 1 with it. My thought was that if the problem went away I could assume it was a bad plug. If the misfire issue switched to cylinder 1 then I could assume it was the coil.
Surprisingly, when I put it all back together and cleared the codes the misfire error came back again on cylinder 2.
Any suggestions on what else I should be looking for?
When the engine is running at idle, if I give it a little throttle it does sound like maybe some air is leaking (or maybe just the sound caused by a misfire)?
I have read a vacuum leak could be to blame - but not sure what/where I would look for that. Any thoughts or assistance would be greatly appreciated!
If it's like my nightmare with my 2016 GLE350, it could be a fuel injector. My saga involved a fuel pressure code that also involved the high-pressure fuel pump.
I would add that when I went with a Bosch replacement, the dealer said my plugs were fouled and replaced them with MB plugs.
Not sure if this will help but.... I had the same issues with cylinder 1 on my w166 ml500 (278 motor). Also swappedf coil and plugs to no avail. Mechanic said it was carbon build up causing a sticky valve. Ran a valve seat cleaner through the car and it fixed it. Out of curiosity. When #2 is missing do you get better fuel economy? Cheers
It might be the photo, but it looks like the grey latches are not fully latched. This may or may not cause misfire, but to rule out bad coil connection the connector needs to be fully seated and latched.
Are you completely clear on how the connector and latches operate? They are tricky when first learning them.
So it's been a few days. I finally was able to get back to it. I replaced all the plugs (#2 was definitely fouled), swapped all coils over 1 cylinder, changed the oil, and put it all back together. Same issue. I also ensured the coil was firmly seated and connector tight and latched.
I did a little more troubleshooting with Xentry, and the only issue the quick test comes back with is a cylinder 2 misfire. I cleared the faults and re-read to ensure. Code came back right away (within 10 seconds of starting the car). Attached here is the freeze frame data, a new compression test, and the fuel injector performance data retrieved from Xentry. Most of the data on there means nothing to me, so hoping someone here may be able to help.
Also looking at the "Actual Values" section of Xentry, the only 2 things I was really finding out of range was "Uniformity of lambda control of right cylinder bank", which had a value of 1.74 (specified value should be less than 0.80). The left bank was fine reading a value of 0.30.
The other issue was the rail pressure, which was was reading 201.0 bar (value is specified as 200.0 bar).
I'm at a loss to know what to check next. I suppose I could try a valve seat cleaner as garysymons suggested - though I am afraid to really run it long with the misfire. How much do I need to worry about causing damage with this?
Also, in case this helps, when running at idle, when a give it a little gas it sounds like I can hear rushing/sucking air briefly before the RPMs kick in. Could this be a vacuum leak of some kind?
As always, any ideas are very appreciated!
Last edited by ccrobin; Dec 7, 2022 at 12:04 AM.
Reason: spelling, supplemental info
Not sure if this will help but.... I had the same issues with cylinder 1 on my w166 ml500 (278 motor). Also swapped coil and plugs to no avail. Mechanic said it was carbon build up causing a sticky valve. Ran a valve seat cleaner through the car and it fixed it. Out of curiosity. When #2 is missing do you get better fuel economy? Cheers
Thanks for the suggestion, I haven't run it long enough to know about fuel economy. I suppose I could try the valve seat cleaner. Can you recommend or share the product you used?
So it's been a few days. I finally was able to get back to it. I replaced all the plugs (#2 was definitely fouled), swapped all coils over 1 cylinder, changed the oil, and put it all back together. Same issue. I also ensured the coil was firmly seated and connector tight and latched.
I did a little more troubleshooting with Xentry, and the only issue the quick test comes back with is a cylinder 2 misfire. I cleared the faults and re-read to ensure. Code came back right away (within 10 seconds of starting the car). Attached here is the freeze frame data, a new compression test, and the fuel injector performance data retrieved from Xentry. Most of the data on there means nothing to me, so hoping someone here may be able to help.
Also looking at the "Actual Values" section of Xentry, the only 2 things I was really finding out of range was "Uniformity of lambda control of right cylinder bank", which had a value of 1.74 (specified value should be less than 0.80). The left bank was fine reading a value of 0.30.
The other issue was the rail pressure, which was was reading 201.0 bar (value is specified as 200.0 bar).
I'm at a loss to know what to check next. I suppose I could try a valve seat cleaner as garysymons suggested - though I am afraid to really run it long with the misfire. How much do I need to worry about causing damage with this?
Also, in case this helps, when running at idle, when a give it a little gas it sounds like I can hear rushing/sucking air briefly before the RPMs kick in. Could this be a vacuum leak of some kind?
As always, any ideas are very appreciated!
Fouled plug means incomplete combustion which means insufficient spark or too much fuel.
Fouled plug means incomplete combustion which means insufficient spark or too much fuel.
Are the plugs and coils OEM MB parts?
I will look at the data later tonight.
Thanks. Plugs were OEM mercedes, and coils are the factory originals.
I am going to try a valve/top engine cleaner to see if carbon buildup could be the culprit.
I have noticed the issue is less pronounced when starting cold and seems to get worse when warming up. I started and drove it today for about 1 mile to go get the valve cleaner. When I started, the MIL actually went off and the vehicle seemed to drive fine for a bit (albeit a bit noisy - fast ticking sounds like valves ticking or loud injectors). On the way to the auto parts store the MIL stayed off. It did not return until about halfway back home (again, only about a mile total).
Maybe the fresh oil last night had some positive effect? At any rate, I will report back after the top end cleaner is run through it.
Fouled plug means incomplete combustion which means insufficient spark or too much fuel.
Are the plugs and coils OEM MB parts?
I will look at the data later tonight.
So I performed the upper engine clean and added lucas injector cleaner into the fuel. No change. I took it for a 10-15 minute drive after the cleaning - MIL never went off, and had noticeable vibration in the 1500-2000 RPM range when under load. It also runs rough at idle. I also hear what sounds like little pops after revving a bit (as the rpms decline) - I suspect maybe little backfires?
Sadly the Indys near me are all 2-3 weeks out to even look at it. It will really cause some problems for me if I can't get it resolved sooner - though I'm at a loss for what else to check.
I also can't get over thinking there is some sort of vacuum or seal that may be the issue. The short "Fffffffft" sound I hear when I give it a little gas (the split second before the revs start to build) just doesn't seem right - and when it is running it seems more than just running rough - it seems louder.
No other codes are showing in Xentry though, and checking all actual values within Xentry also seem fine (with the exception of the "Uniformity of lambda control of right cylinder bank" and "Rail Pressure" which I mentioned earlier).
In case it gives any better insight, I have attached photos of the old spark plugs. You can see #2 is noticeably fouled compared to the others.
So it's been a few days. I finally was able to get back to it. I replaced all the plugs (#2 was definitely fouled), swapped all coils over 1 cylinder, changed the oil, and put it all back together. Same issue. I also ensured the coil was firmly seated and connector tight and latched.
I did a little more troubleshooting with Xentry, and the only issue the quick test comes back with is a cylinder 2 misfire. I cleared the faults and re-read to ensure. Code came back right away (within 10 seconds of starting the car). Attached here is the freeze frame data, a new compression test, and the fuel injector performance data retrieved from Xentry. Most of the data on there means nothing to me, so hoping someone here may be able to help.
Also looking at the "Actual Values" section of Xentry, the only 2 things I was really finding out of range was "Uniformity of lambda control of right cylinder bank", which had a value of 1.74 (specified value should be less than 0.80). The left bank was fine reading a value of 0.30.
The other issue was the rail pressure, which was was reading 201.0 bar (value is specified as 200.0 bar).
I'm at a loss to know what to check next. I suppose I could try a valve seat cleaner as garysymons suggested - though I am afraid to really run it long with the misfire. How much do I need to worry about causing damage with this?
Also, in case this helps, when running at idle, when a give it a little gas it sounds like I can hear rushing/sucking air briefly before the RPMs kick in. Could this be a vacuum leak of some kind?
As always, any ideas are very appreciated!
I read the data files, they don't help except to say there is a misfire. Compression test is OK, strangely cylinder 2 has the highest value.
Have you done all of the XENTRY tests list under "Engine output"?
The candidates for one cylinder misfire are:
- spark plug
- fuel injector
- ignition coil
Sensor failure (cam position, cam magnet, crank position, air or water temp) would not affect one cylinder. Mechanical failure in the variable cam system would affect more than one cylinder.
I read the data files, they don't help except to say there is a misfire. Compression test is OK, strangely cylinder 2 has the highest value.
Have you done all of the XENTRY tests list under "Engine output"?
The candidates for one cylinder misfire are:
- spark plug
- fuel injector
- ignition coil
Sensor failure (cam position, cam magnet, crank position, air or water temp) would not affect one cylinder. Mechanical failure in the variable cam system would affect more than one cylinder.
As always, triple and quadruple check your work.
Thanks. I'll check everything again and report. I was thinking the same - it has to be something simple I am overlooking. I haven't actually swapped the fuel injectors yet as it looks like a bugger to get at it all. Is there any other way to effectively test the injectors while in the vehicle?
Also wondering if there is a way to test the coil connector itself? Can I use a spark plug tester to see if the coil is generating a spark to the plug (haven't used one of those since my old carbureted cars - just not sure of that is safe on a modern vehicle)? Since I know the coil works this could help identify a faulty connection.
Check in XENTRY for fuel injector tests. I saw a test on the list in one of the files you posted. Is there a "turn on-turn off" test for injectors in XENTRY?
If #2 plug is fouled you need to find why. Insufficient spark (plug, coil, harness connector) or injector are the only possibilities. A sensor or ECU are ruled out because there are no misfires on other cylinders.
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GLE 350 Cylinder 2 Misfire - replaced plug, swapped coil - still happening
