Fuel Trim Range
#1
Thread Starter
Member
Joined: Oct 2017
Posts: 187
Likes: 11
2010 C63 AMG, 2015 GL450, 2018 GLS 550, 2021 GLS 450
Fuel Trim Range
What is the proper fuel trim for the M156?
I plugged in my cheap BT scanner and got a fuel trim level of -95 for Bank 1 and 1 for Bank 2. I confirmed this with a mechanic level scan tool that I borrowed from a friend
No CEL is on.
Now my reason for checking this, I hear a light plastic on plastic or rubber on rubber tick/knock at idle. The sound occurs regardless of the engine temp, and disappears if the accelerator pedal is depressed at all. The sound sometimes goes away if I fully depress the brakes. The sound isn’t audible in the engine bay only the cabin, and there are some days where the sound never occurs.
I plugged in my cheap BT scanner and got a fuel trim level of -95 for Bank 1 and 1 for Bank 2. I confirmed this with a mechanic level scan tool that I borrowed from a friend
No CEL is on.
Now my reason for checking this, I hear a light plastic on plastic or rubber on rubber tick/knock at idle. The sound occurs regardless of the engine temp, and disappears if the accelerator pedal is depressed at all. The sound sometimes goes away if I fully depress the brakes. The sound isn’t audible in the engine bay only the cabin, and there are some days where the sound never occurs.
#3
Thread Starter
Member
Joined: Oct 2017
Posts: 187
Likes: 11
2010 C63 AMG, 2015 GL450, 2018 GLS 550, 2021 GLS 450
Can I go to a bigger Injector size without a tune/is it worth it?
#4
What injectors did you put in there? you are running really rich.
#7
That's what I thought at first, but a post MAF air leak should cause a high positive fuel trim, and he's saying it's negative. I also just noticed that the issue is just on one bank. It actually might be an injector stuck open, or a bad O2 sensor.
EDIT: ....or a bad MAF. You should be able to check the air flow readings on both banks with your scan tool. They should read similar voltage at idle if both MAFs are in good working order.
EDIT: ....or a bad MAF. You should be able to check the air flow readings on both banks with your scan tool. They should read similar voltage at idle if both MAFs are in good working order.
Last edited by BalanBro; 01-31-2020 at 02:00 PM.
Trending Topics
#8
The ECU thinks there's way too much fuel on that bank so it's trying to remove fuel with the negative trim.
It either actually has too much fuel or not enough air. Or whatever is reading the output thinks that.
It either actually has too much fuel or not enough air. Or whatever is reading the output thinks that.
#9
Thread Starter
Member
Joined: Oct 2017
Posts: 187
Likes: 11
2010 C63 AMG, 2015 GL450, 2018 GLS 550, 2021 GLS 450
That's what I thought at first, but a post MAF air leak should cause a high positive fuel trim, and he's saying it's negative. I also just noticed that the issue is just on one bank. It actually might be an injector stuck open, or a bad O2 sensor.
EDIT: ....or a bad MAF. You should be able to check the air flow readings on both banks with your scan tool. They should read similar voltage at idle if both MAFs are in good working order.
EDIT: ....or a bad MAF. You should be able to check the air flow readings on both banks with your scan tool. They should read similar voltage at idle if both MAFs are in good working order.
#10
MBWorld Fanatic!
Joined: Jun 2008
Posts: 8,068
Likes: 2,849
From: Los Angeles
2012 P31 C63 Coupe Trackrat, 2019 GLE63S Coupe Beast
#12
post pictures...honestly don't think -95 is possible without fault and limp mode.
do you have Torque for Android?
do you have Torque for Android?
#13
#14
Thread Starter
Member
Joined: Oct 2017
Posts: 187
Likes: 11
2010 C63 AMG, 2015 GL450, 2018 GLS 550, 2021 GLS 450
#15
if the ECU cannot correct quickly or enough at enough data points...usually at throttle tip in. it'll throw into limp mode.
if true, at -95...if you reset all adaptations, you'll have a very tough time starting your engine without giving it gas while cranking.
with 596cc injectors the largest long term fuel trim i ever saw on a stock injector tune was -35%. only for a short while. not sure what the combined long term and short term was.
-95 is pretty nuts.
if true, at -95...if you reset all adaptations, you'll have a very tough time starting your engine without giving it gas while cranking.
with 596cc injectors the largest long term fuel trim i ever saw on a stock injector tune was -35%. only for a short while. not sure what the combined long term and short term was.
-95 is pretty nuts.
#16
can you separate Long Term Fuel Trims and Short Term Fuel trims
maybe you're displaying combination of both LTFT and STFT. can't really tell from the screenshot.
maybe you're displaying combination of both LTFT and STFT. can't really tell from the screenshot.
#17
Thread Starter
Member
Joined: Oct 2017
Posts: 187
Likes: 11
2010 C63 AMG, 2015 GL450, 2018 GLS 550, 2021 GLS 450
#19
like this...
#20
yeah you have a leak or some mechanical issue. if its your STFT and not your LTFT has corrections and your Manifold readout is wrong as BLKROKT stated
Last edited by hachiroku; 01-31-2020 at 05:45 PM.
#21
Thread Starter
Member
Joined: Oct 2017
Posts: 187
Likes: 11
2010 C63 AMG, 2015 GL450, 2018 GLS 550, 2021 GLS 450
Mechanically I’m pretty solid I think. No oil consumption/blue smoke.
Service A was completed at the beginning of this month, where I was advised the following:
Rear brake pads at 4mm: Done myself
Air filter based on Wear/Mileage: Not done yet
Spark Plugs based on Wear/Mileage: Not done yet
Transmission Fluid change due by June: Not done yet.
The weird part is that the car definitely isn’t down on power, there’s just a strange noise in the cabin.
#22
Thread Starter
Member
Joined: Oct 2017
Posts: 187
Likes: 11
2010 C63 AMG, 2015 GL450, 2018 GLS 550, 2021 GLS 450
#23
You have a leak in the intake manifold. I had the exact same issue a couple months ago. Was going crazy. I had new injectors. New o2’s. New intake mainifold gasket+pcv valve.
One bank was running lean. The other rich. Took the manifold off and smoke tested it on bench. Found the problem... rear of the manifold was leaking
One bank was running lean. The other rich. Took the manifold off and smoke tested it on bench. Found the problem... rear of the manifold was leaking
#24
Thread Starter
Member
Joined: Oct 2017
Posts: 187
Likes: 11
2010 C63 AMG, 2015 GL450, 2018 GLS 550, 2021 GLS 450
You have a leak in the intake manifold. I had the exact same issue a couple months ago. Was going crazy. I had new injectors. New o2’s. New intake mainifold gasket+pcv valve.
One bank was running lean. The other rich. Took the manifold off and smoke tested it on bench. Found the problem... rear of the manifold was leaking
One bank was running lean. The other rich. Took the manifold off and smoke tested it on bench. Found the problem... rear of the manifold was leaking
How do I prep the surface that mates with the manifold?
#25
check this thread out. https://mbworld.org/forums/c63-amg-w...valve-diy.html