2008 E350 Misfire....another one
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Newbie
Joined: Dec 2020
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E350
2008 E350 Misfire....another one
Struggling with this for a year. Two independent shops. One said yes we can help, then said nope need to find a Mercedes speciality shop.
Located a specialty shop. ECU replaced, MAF, nope. Then said it has to be coils, All coils replaced, three times by me(they claimed I received counterfeit coils from Amazon). Replaced All plugs.
Replaced Fuel pumps, claimed fuel pressure was low.
Still get a random misfire. Nothing that can be identified or tracked. May run 1k miles perfect or 1 mile. Turn off engine, it clears and off you go.
Took it to Mercedes. Said battery is weak. They replaced it. I said keep it, drive it. Sure enough she misfires.
Diagnosed as bad engine wire harness.
$5200.00. Far exceeds value of car.
I can work on it.
I searched forums, doesn't seem to be common problem, or am I missing something.
Any wire harness repair companies?
I am considering used harnesses.
Guidance? Suggestions?
Obviously I plan on having a discussion with dealer about diagnosis......
Located a specialty shop. ECU replaced, MAF, nope. Then said it has to be coils, All coils replaced, three times by me(they claimed I received counterfeit coils from Amazon). Replaced All plugs.
Replaced Fuel pumps, claimed fuel pressure was low.
Still get a random misfire. Nothing that can be identified or tracked. May run 1k miles perfect or 1 mile. Turn off engine, it clears and off you go.
Took it to Mercedes. Said battery is weak. They replaced it. I said keep it, drive it. Sure enough she misfires.
Diagnosed as bad engine wire harness.
$5200.00. Far exceeds value of car.
I can work on it.
I searched forums, doesn't seem to be common problem, or am I missing something.
Any wire harness repair companies?
I am considering used harnesses.
Guidance? Suggestions?
Obviously I plan on having a discussion with dealer about diagnosis......
Out Of Control!!
Joined: Apr 2019
Posts: 12,002
Likes: 6,827
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
kill the parts canon
> RANDOM MISFIRINGS beyond common basics:
The harness issue you mention is called "oil in harness" - See if you find evidence of oil at ECU ... Knowing you already have a new ECU, we won't change itfor no reason
else use your scanner to read live LT FUEL TRIMS at warmed-up idle... what numbers, negatives?
+++ Key restart clears misfires...
That can be caused by a crazy module on CAN-C or a gateway - Let's get a list of current + stored faults .
FYI :
"Stored" simply means not current. Either passed or TRANSIENT ie. it can be current but not "non-stop". So we pay attention to "stored" faults just as well as "current"!
Transient are caused by poor bus transmissions some of us are familiar with.
Let's see what we have here.
The harness issue you mention is called "oil in harness" - See if you find evidence of oil at ECU ... Knowing you already have a new ECU, we won't change itfor no reason
else use your scanner to read live LT FUEL TRIMS at warmed-up idle... what numbers, negatives?
+++ Key restart clears misfires...
That can be caused by a crazy module on CAN-C or a gateway - Let's get a list of current + stored faults .
FYI :
"Stored" simply means not current. Either passed or TRANSIENT ie. it can be current but not "non-stop". So we pay attention to "stored" faults just as well as "current"!
Transient are caused by poor bus transmissions some of us are familiar with.
Let's see what we have here.
Last edited by CaliBenzDriver; Sep 3, 2023 at 06:08 PM. Reason: transient
Out Of Control!!
Joined: Apr 2019
Posts: 12,002
Likes: 6,827
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
collection
ok, i read through your whole collection of faults...
what I see is just about all cylinders misfire (no isolated) then you have seatbelt tensioner issue and the most interesting the SBC module which I believe shares CAN-C bus with ECU (double check).
Next look at live fuel trim data on warm idling engine to note LONG-TERM FUEL TRIM ...
Last you go ahead and reset/clear all faults and see what faults comes back after a short while (this clears fuel trim as well).
Don't forget to investigate "oil in harness" at ECU for contamination.
After the reset procedure do you feel the misfires right away at idle or when, how soon does misfire condition returns?
✌️
what I see is just about all cylinders misfire (no isolated) then you have seatbelt tensioner issue and the most interesting the SBC module which I believe shares CAN-C bus with ECU (double check).
Next look at live fuel trim data on warm idling engine to note LONG-TERM FUEL TRIM ...
Last you go ahead and reset/clear all faults and see what faults comes back after a short while (this clears fuel trim as well).
Don't forget to investigate "oil in harness" at ECU for contamination.
After the reset procedure do you feel the misfires right away at idle or when, how soon does misfire condition returns?
✌️
Thread Starter
Newbie
Joined: Dec 2020
Posts: 9
Likes: 2
E350
Follow Up Misfire
"After the reset procedure do you feel the misfires right away at idle or when, how soon does misfire condition returns?"
After I reset either with scanner or turning engine off and several occasions having adaptions reset, there is absolutely no pattern. The misfires may not return for up to 1k miles. Or may return pulling out of the driveway. Weather does not seem to affect or cause misfire. Local driving or Highway driving no affect. Excessive acceleration or old man driving no affect. Sometimes turning car off and restarting only last one mile, other times days. Ambient temperature, engine temperature no affect. I have let it idle and jiggled shook every connection I can see.
When I pick it up from the dealership on Tuesday will check for oil.
I hope if the dealership has identified the harness as bad, they should be able to tell me what was/is the isolated problem........
As always I appreciate the guidance and help!
After I reset either with scanner or turning engine off and several occasions having adaptions reset, there is absolutely no pattern. The misfires may not return for up to 1k miles. Or may return pulling out of the driveway. Weather does not seem to affect or cause misfire. Local driving or Highway driving no affect. Excessive acceleration or old man driving no affect. Sometimes turning car off and restarting only last one mile, other times days. Ambient temperature, engine temperature no affect. I have let it idle and jiggled shook every connection I can see.
When I pick it up from the dealership on Tuesday will check for oil.
I hope if the dealership has identified the harness as bad, they should be able to tell me what was/is the isolated problem........
As always I appreciate the guidance and help!
Thread Starter
Newbie
Joined: Dec 2020
Posts: 9
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E350
Update
Vehicle picked up from dealer. Dealer confident the misfire is not mechanical.
Dealer said no oil in harness.
Dealer cannot point to specific area or spot on harness where the problem may be. Dealer felt by removing harness I will probably find an area of a problem. Obviously they want to replace with new.
But I do have a new $500 dollar installed battery. In reality not bad since they installed the battery I didn't have to pay diagnostic fees.
Dealer said no oil in harness.
Dealer cannot point to specific area or spot on harness where the problem may be. Dealer felt by removing harness I will probably find an area of a problem. Obviously they want to replace with new.
But I do have a new $500 dollar installed battery. In reality not bad since they installed the battery I didn't have to pay diagnostic fees.
Newbie
Joined: Sep 2023
Posts: 6
Likes: 0
2008 E350 4matic
Hopefully, you will figure it out. I had a similar issue although on a .....2011 535 BMW. Did everything you did coils and plugs etc. and it really turned out for me on the BMW, (I know not the same) that it was one of the GDI injectors. Had to replace an injector and get it coded. I think you have eliminated plugs and coils and ecu, but the ignition is a timing event with air, spark and fuel happening at the exact moment. Something is throwing off the amount of fuel entering or electronically when it is supposed to happen. Mine is a semi educated guess and I know much more versed people here. GL
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Out Of Control!!
Joined: Apr 2019
Posts: 12,002
Likes: 6,827
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Vehicle picked up from dealer.
Dealer confident the misfire is not mechanical.
Dealer said no oil in harness.
Dealer cannot point to specific area or spot on harness where the problem may be.
Dealer felt by removing harness I will probably find an area of a problem. Obviously they want to replace with new.
....
Dealer confident the misfire is not mechanical.
Dealer said no oil in harness.
Dealer cannot point to specific area or spot on harness where the problem may be.
Dealer felt by removing harness I will probably find an area of a problem. Obviously they want to replace with new.
....
there is no evidence found of "oil in harness" ...
I would try to narrow down your list of faults for unstable module on the ECU CAN-C.
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