2015 ML400 4MATIC misfiring
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2015 ML400 4MATIC
2015 ML400 4MATIC misfiring
Hello everyone, I need help. I have a 2015 ML400 4MATIC. It has 86500 miles. It’s having multiple random misfires. I pulled codes P0300, P0304 and P0305 (permanent codes). I changed all spark plugs and ignition coils. It’s still misfiring and showing same codes (permanent codes). Engine runs shaky and rough very noticeable when idling(check engine light flashes when idling or going2-5mph), also it seems to be getting worse the longer it runs at lower speeds. When pressing gas and going on higher speeds, it acts fine (check engine light is present but NOT flashing). However there’s a very very minor shake when driving.
please let me know if you had a similar issue and what to do, thank you.
please let me know if you had a similar issue and what to do, thank you.
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hey @davidabd24 did you end up finding the issue did you end up finding the cause please let me know thankyou!
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W212 MY'14 M276-3.5NA @75kMi
pointers
hey @davidabd24 did you end up finding the issue did you end up finding the cause please let me know thankyou!
-- 1st step ignition: plugs + boots + coils ... not 1 cyl. but all equally new to keep engine balanced.
Pay attention to :
- chassis faults,
- fuel pressure,
- fuel trims
- and... stable voltage!
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so i have ml350 2015 has po300 and po305 code i changed ignition coil and spark plug the code did not go away i took it to mechanic thinking that would be last option cause i was clueless but long story short he told me that the ecm is bad the car only has 89000 miles on it..
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W212 MY'14 M276-3.5NA @75kMi
so i have ml350 2015 has po300 and po305 code i changed ignition coil and spark plug the code did not go away i took it to mechanic thinking that would be last option cause i was clueless but long story short he told me that the ecm is bad the car only has 89000 miles on it..
Double check oil in harness at all Cam Pos. Sensors and Lambdas for oil.
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W212 MY'14 M276-3.5NA @75kMi
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
... finding dry CPS is very odd!
If we recap you have a Cyl.5 low contribution code at 90k
You've proven its not ignition
You've proven not oil-in-harness
I don't have high hopes on new injector
>> You need BORE SCOPE for dry cylinder walls damage.
"Better oiling" would have prevented that earlier on.
If we recap you have a Cyl.5 low contribution code at 90k
You've proven its not ignition
You've proven not oil-in-harness
I don't have high hopes on new injector
>> You need BORE SCOPE for dry cylinder walls damage.
"Better oiling" would have prevented that earlier on.
Last edited by CaliBenzDriver; Jan 10, 2025 at 04:53 PM.
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so the front timing covers on which camshafts magnets sit on are leaky but the camshaft magnets themselves i dont see problem with the oil level is also at max as i said the shop told me to install ecu on it thats my option for now for a engine that only has 89000 miles it shouldnt have any engine damage
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2017 GLE350 4MATIC
so the front timing covers on which camshafts magnets sit on are leaky but the camshaft magnets themselves i dont see problem with the oil level is also at max as i said the shop told me to install ecu on it thats my option for now for a engine that only has 89000 miles it shouldnt have any engine damage
Last edited by chassis; Jan 10, 2025 at 08:39 PM.
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W212 MY'14 M276-3.5NA @75kMi
so the front timing covers on which camshafts magnets sit on are leaky but the camshaft magnets themselves i dont see problem with the oil level is also at max as i said the shop told me to install ecu on it thats my option for now for a engine that only has 89000 miles it shouldnt have any engine damage
Personally I think it's more likely the other way around:
Bad Cyl.5 bore + Good ECU.
So I recommend TESTING cyl.5:
compression... drafty
bore scope.... scoring
relative crank... low speeds
Let's see what quick testing shows - Zero good reason for random guess with expensive parts. You found no oil pointing at ECU. Your COPS have integrated MOSFET drivers.
You can very well get the ECU replaced as shop recommends or trigger yours to relearn better timings if bores are nearly ok.
Last edited by CaliBenzDriver; Jan 10, 2025 at 06:35 PM.
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2017 GLE350 4MATIC
I am aware of no confirmed cases of bore scoring on M276.
There are no conclusively verified ECU failures which were not related to oil infiltration.
Start with the obvious and easy things. Separate each of the 8 cam-related wiring connectors and post the photos here.
There are no conclusively verified ECU failures which were not related to oil infiltration.
Start with the obvious and easy things. Separate each of the 8 cam-related wiring connectors and post the photos here.
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2015 ML350 misfire
hey guys so i took the ecu out and i found oil on the first ecu connector which brings me to conclusion that mechanic was right i still need to inspect my cps sensor for oil but i already say the camshaft magnets their connectors dont have oil in them its crazy how oil can go from connector to the engine wiring harness can you guys also tell me more location oil can come from on m276 engine.
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W212 MY'14 M276-3.5NA @75kMi
big ticket
hey guys so i took the ecu out and i found oil on the first ecu connector which brings me to conclusion that mechanic was right i still need to inspect my cps sensor for oil but i already say the camshaft magnets their connectors dont have oil in them its crazy how oil can go from connector to the engine wiring harness can you guys also tell me more location oil can come from on m276 engine.
Oil is known to be insulant (not conductor) but somehow when it gets to an ECU things stop going well...
-- The standard oil source are the seasoned Continental cam sensors.
"Magnets" are usually immune because cooler.
Other engine sensors can leak oil in harness:
the oil pump solenoid has been shown to leak oil
the pil level sendor has been shown to leak oil
Upstream Lambda + downstream O2 sensors do receive oil through harness.
No1 issue being that... the whole engine harness needs replacement.
That's a standard $10,000 job.
If only sensors and ECU are replaced: harness will refill them with already stored oil.
What may prevent that expense is ECU + lambda pigtails.
Last edited by CaliBenzDriver; Jan 15, 2025 at 05:48 PM.
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2017 GLE350 4MATIC
Oil as an insulator creates problems when a film
of oil coats the contacts between the cam sensor and harness, and between the harness and ECU, or both. An oil film is created when the cam sensor housing is compromised allowing oil to infiltrate the sensor internals and is transported into the harness via capillary action. Contact pairs are coated in this process with a film of insulating oil causing intermittent connectivity between the ECU and sensors. And magnets, O2 sensors and injectors in severe cases.
of oil coats the contacts between the cam sensor and harness, and between the harness and ECU, or both. An oil film is created when the cam sensor housing is compromised allowing oil to infiltrate the sensor internals and is transported into the harness via capillary action. Contact pairs are coated in this process with a film of insulating oil causing intermittent connectivity between the ECU and sensors. And magnets, O2 sensors and injectors in severe cases.
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is there a way to fix without changing the engine control unit harness like cleaning and checking ocassionally for oil and stuff im going to change all cam sensors im pretty sure they are the reason for this as long as it recieves timely cleaning it should be fine right by the time little oil left in the cable finishes
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ML400 - 128i - Atlas VR6
Just a thought. What if one were to very carefully detail each wire and pin on the harness connector going to the ECU and cut it off and rewire. Effectively making the wires going into the ECO dry.
And also put in place all the necessary sacrificial connectors to prevent further oil wicking up.
And also put in place all the necessary sacrificial connectors to prevent further oil wicking up.
Out Of Control!!
Joined: Apr 2019
Posts: 11,958
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Just a thought. What if one were to very carefully detail each wire and pin on the harness connector going to the ECU and cut it off and rewire. Effectively making the wires going into the ECU dry.
And also put in place all the necessary sacrificial connectors to prevent further oil wicking up.
And also put in place all the necessary sacrificial connectors to prevent further oil wicking up.
