When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
im getting -ve LTFT on my w204 c63 around -17 ish on both banks and stft of -78 to -1.56 inhave replaced both mafs new intake maan filters, 02 seems to be working good values look normal, car drives good idling normal driving is smooth wot is good and strong,
i have low AC refrigerant which might be caused by a leakage some where which i have to gwt fixed other wise car is normal.
anyone suggest what could be causing this negative long term fuel trim?
A few months back I put new lifters in the left bank as they were 3 of them were ticking and followed all timing procedures accordingly to the factory manual with the timing tools.
My LTFT stayed in negative so further investigation i checked the cam shaft timing from my scanner and the timing isnt staying still its supposed to be 28 for the intake and -15 for the exhaust as per mb manual
But my timing is constantly moving even after doing relearning its still moving up and down both bank
What could be causing this could this be cause of the negative trims? Or are these readings normal i.e non static and are +- 1 degree on idle?
A few months back I put new lifters in the left bank as they were 3 of them were ticking and followed all timing procedures accordingly to the factory manual with the timing tools.
My LTFT stayed in negative so further investigation i checked the cam shaft timing from my scanner and the timing isnt staying still its supposed to be 28 for the intake and -15 for the exhaust as per mb manual
But my timing is constantly moving even after doing relearning its still moving up and down both bank
What could be causing this could this be cause of the negative trims? Or are these readings normal i.e non static and are +- 1 degree on idle?
When I deleted my EVAP system I started having issues with negative LTFT's, it had to be corrected by my tuner to get them back to normal.
I'd look into making sure all of your EVAP and PCV system are plugged in and working correctly.
EVAP system seemed to ticking and working okay no codes related to EVAP but ill check the connection again, i disconnected the Evap switch and the negative trims started to come down, dont know if this is useful information or not.
im getting -ve LTFT on my w204 c63 around -17 ish on both banks and stft of -78 to -1.56 inhave replaced both mafs new intake maan filters, 02 seems to be working good values look normal, car drives good idling normal driving is smooth wot is good and strong,
i have low AC refrigerant which might be caused by a leakage some where which i have to gwt fixed other wise car is normal.
anyone suggest what could be causing this negative long term fuel trim?
thanks
I have an extremely hard time both banks share the exact same lean LTFT in closed loop - I think the scanner support for your engine is wasting your time. matched lean LTFT....
I have an extremely hard time both banks share the exact same lean LTFT in closed loop - I think the scanner support for your engine is wasting your time. matched lean LTFT....
Buy a LAUNCH MB Elite or better
Car usually starts with -15 trims then after driving og 10 miles or so and idling of 30mins or so do they come down , negative trims are not matched they change its just a coincidence that on this screen shot they are same,
my fuel trims are showing rich not lean as they are negative meaning car is rich, here is another screenshot after the car is fully warmed up and idling for 30mins
Car usually starts with -15 trims then after driving og 10 miles or so and idling of 30mins or so do they come down , negative trims are not matched they change its just a coincidence that on this screen shot they are same,
my fuel trims are showing rich not lean as they are negative meaning car is rich, here is another screenshot after the car is fully warmed up and idling for 30mins
Yep, so now you need to find out why your ECU is removing fuel from your engine combustion, more or less equally on both banks....
What's particular about your engine to cause this lean?
Yep, so now you need to find out why your ECU is removing fuel from your engine combustion, more or less equally on both banks....
What's particular about your engine to cause this lean?
from what people have told me is that when a car doesn't get enough air it is when the trims go negative as the ecu see that more fuel is being added then needed so it removes that fuel.
how do i figure this out?? That is why i posted on this forum so someone can tell me what going on???
car drives normal , power is good.
New MAFs installed new air filters installed, fuel pressure is good , o2 voltage seem to be good and they are more or less working on same voltage.
from what people have told me is that when a car doesn't get enough air it is when the trims go negative as the ecu see that more fuel is being added then needed so it removes that fuel.
how do i figure this out?? That is why i posted on this forum so someone can tell me what going on???
car drives normal , power is good.
New MAFs installed new air filters installed, fuel pressure is good , o2 voltage seem to be good and they are more or less working on same voltage.
so i dont know what to look for next.
It's pretty unusual for an engine not to get enough air.
If your intake is particularly dirty , throttle plate could use cleaning spray or you have broken intake flaps issues.
Lets check on IGN:
Spark ignition issues more likely except you say power is good and scanner has no misfires faults...
How old are those sparkplugs?
Last edited by CaliBenzDriver; Jul 14, 2024 at 07:02 PM.
It's pretty unusual for an engine not to get enough air.
If your intake is particularly dirty , throttle plate could use cleaning spray or you have broken intake flaps issues.
Lets check on IGN:
Spark ignition issues more likely except you say power is good and scanner has no misfires faults...
How old are those sparkplugs?
Plugs are like maybe 18k miles old they might need changing?
yes no cels , also i have noticed that when the engine is colder or being warmed up the car is more towards negative trims like -15 on idle and as the car warms up and i drive for a bit and let it idle for 10 to 15 mins the trims come down to -8ish
its very odd , i have checked everything expect for the spark plugs.
Could be leaky injectors which is some what common.
thats the 1st thing i changed with my friends c63 and the LTFT remained the same and his car had normal LTFts , im still rocking his injections also my injections have been tested and passed.
Last edited by wheelspk2131; Jul 15, 2024 at 11:31 AM.
The key here is LTFT are nearly equal so it's unlikely one cylinder having issues... not a plug, coil or injector.
It's something common to both Banks causing your lean trim response... the engine combustion is too rich.
I understand you are saying you are still running your friends injectors... these must be paired individually to the engine ECU.
Even that may not provide relief because lean was present before injector shuffling...
How is the engine blow-by pressure vs. PCV status ?? easy quick fix
> Check/replace the vaccum pump small check valve (shown above) that works the flaps actuators full of oil ?
Even if i put my injector back the negative fuel teims remain on idle.
is this the valve you talking about? The ones you posted are for w205 mine is a w204 c63
Also i have a heavy power steering since many months could that be causing issues???
i have noticed when i press/pump the break my short term trims for positive for 3 to 4 seconds and the long term also drop , how is the break related to fuel teims?
Last edited by wheelspk2131; Jul 15, 2024 at 06:07 PM.
Even if i put my injector back the negative fuel teims remain on idle.
is this the valve you talking about? The ones you posted are for w205 mine is a w204 c63
Also i have a heavy power steering since many months could that be causing issues???
i have noticed when i press/pump the break my short term trims for positive for 3 to 4 seconds and the long term also drop , how is the break related to fuel teims?
Is your brake vacuum booster operated by a vacuum pump or by engine intake vacuum?
I think pump!
pump shares vacuum with intake flap actuator.
There maybe something to do with crankcase pressure + PCV.
Put stock airboxes on the car if your running row boxes and if that don't work start with a stock tune on the car.
Are you sure you put the right injectors in the car? Do you have alot of black smoke and how is your mpgs
my car 100% stock since its jdm c63 (RHD) it doesn’t come with charcoal filters dont know what ROW airbox are tho , by stock tune do you mean get it tuned?
yea 110% sure the injectors are stock and plus im running injectors off my friends c63 too see if that solves my problem and his car is also stock c63 so thats out of question that the injectors are not stock,
zero black smoke and MPG is horrible just like every c63 😂
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
