Negative Fuel trims
Thread Starter
Junior Member
Joined: Mar 2024
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c63 w204
As the car had -25 negative trims before i changed the MAFs , injections and the filters now -14 negative trim could the oil be contaminated with fuel?? Causing the trims to remain negative still?
my spark plugs are 18k miles old could worn spark plugs cause negative trims?? I have no misfire or codes .
my spark plugs are 18k miles old could worn spark plugs cause negative trims?? I have no misfire or codes .
Out Of Control!!
Joined: Apr 2019
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
intake flaps
Overall this means ECU Lambda are respondive and in good shape.
I would check the intake plenum flaps are operational (not the throttle body). Use the scanner to actuate flaps for testing.
I would check the intake plenum flaps are operational (not the throttle body). Use the scanner to actuate flaps for testing.
Thread Starter
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c63 w204
also i have noticed the car usually starts around -15ish LTFT and as the car warms up and i drive for about 10miles or so and the let the car idle for 10 to 15 mins the LTFT drop to -9 to - 10 I wound if the spark plugs have gone weak?? Or the oil is contaminated with fuel when the car had super negative -25 to -30 previously i have not changed the oil yet
Out Of Control!!
Joined: Apr 2019
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
the intake manifold has been replaced with a donor car, the flaps are working as they should be,
also i have noticed the car usually starts around -15ish LTFT and as the car warms up and i drive for about 10miles or so and the let the car idle for 10 to 15 mins the LTFT drop to -9 to - 10
I wound if the spark plugs have gone weak??
Or the oil is contaminated with fuel when the car had super negative -25 to -30 previously i have not changed the oil yet
also i have noticed the car usually starts around -15ish LTFT and as the car warms up and i drive for about 10miles or so and the let the car idle for 10 to 15 mins the LTFT drop to -9 to - 10
I wound if the spark plugs have gone weak??
Or the oil is contaminated with fuel when the car had super negative -25 to -30 previously i have not changed the oil yet
It sounds like the fuel map have been altered and now your ECU is leaning your mixture as a result.
I just saw this post that can help you reset the bugs out of your ECU. Let me find that post... here.
Last edited by CaliBenzDriver; Jul 17, 2024 at 12:30 PM.
Thread Starter
Junior Member
Joined: Mar 2024
Posts: 46
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c63 w204
Engine oil and cold engine trim are unlikely related to your fuel trims issue.
It sounds like the fuel map have been altered and now your ECU is leaning your mixture as a result.
I just saw this post that can help you reset the bugs out of your ECU. Let me find that post... here.
It sounds like the fuel map have been altered and now your ECU is leaning your mixture as a result.
I just saw this post that can help you reset the bugs out of your ECU. Let me find that post... here.
Ill have a-look at the post thanks !
Its really weird why my car has negative trims its literally telling the ecu that its not getting enough air and too much fuel and ecu ia pulling 15% (-15) fuel its so weird …all other readings are in spec 🤦🏽🤦🏽🤦🏽
as as i said previously the car has never been tuned or modified in any way , its 100% stock .
Last edited by wheelspk2131; Jul 17, 2024 at 04:51 PM.
Out Of Control!!
Joined: Apr 2019
Posts: 12,003
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
RICH ENGINE....
Ill have a-look at the post thanks !
Its really weird why my car has negative trims its literally telling the ecu that its not getting enough air and too much fuel and ecu ia pulling 15% (-15) fuel its so weird …all other readings are in spec 🤦🏽🤦🏽🤦🏽
as as i said previously the car has never been tuned or modified in any way , its 100% stock .
Its really weird why my car has negative trims its literally telling the ecu that its not getting enough air and too much fuel and ecu ia pulling 15% (-15) fuel its so weird …all other readings are in spec 🤦🏽🤦🏽🤦🏽
as as i said previously the car has never been tuned or modified in any way , its 100% stock .
Something is causing your ECU LEAN OUT...
Then re-tune your injectors for a chance to fix/improve engine response.
Last edited by CaliBenzDriver; Jul 17, 2024 at 05:54 PM.
Thread Starter
Junior Member
Joined: Mar 2024
Posts: 46
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c63 w204
Out Of Control!!
Joined: Apr 2019
Posts: 12,003
Likes: 6,827
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Each individual injector is adapted to its cylinder during installation. This is done using Xentry tool, I think some other scanner do that as well.
Thing is your lean condition started befored you shuffled injector parts, right?
Thing is your lean condition started befored you shuffled injector parts, right?
Last edited by CaliBenzDriver; Jul 18, 2024 at 12:37 PM.
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Thread Starter
Junior Member
Joined: Mar 2024
Posts: 46
Likes: 2
c63 w204
do you know how to adapt injector to each cyliner? I will do it as my friend had xentry
yes the negative trims were present before i installed new injectors but that maybe was due to bad MAFs
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From: New Jersey/Philly
2010 E350 Coupe
Even before joining, I've noticed this forum is full of juicy cliffhangers but there is never a final chapter to the story.
How did you end up with your M156? I have a very similar saga unfolding with a 3.5L M272 and today have seen my first "normal" fuel trims in ages after doing an oil change and oddly enough, cleaning my upstream 02's electrical connectors with contact cleaner. That of course, is just today however.
How did you end up with your M156? I have a very similar saga unfolding with a 3.5L M272 and today have seen my first "normal" fuel trims in ages after doing an oil change and oddly enough, cleaning my upstream 02's electrical connectors with contact cleaner. That of course, is just today however.
