Help needed please, High negative short term fuel trims
 

Hey good day everyone,


I’ve been having A issue with my car running Rich with high negative STFT (-25/30%) while cruising, also unusually rich AFR’s (10.0/10.5) on initial deceleration

At WOT the cat runs normal Afr’s. Until recently starting to break up

This all started after I repaired a fuel leak from one of my gdi injectors, the leak was from the “o”ring at the top of the injector being pinched, repaired it without taking out the gdi injector. Ever since this repair I have generated the issue.

I’ve back check everything and can’t seem to find any vacuum leaks or errors I may have done while doing the fuel leak repair.

Now my car has been down for about three months now because I can’t seem to identify the cause of this issue. I’m hoping someone can help my diagnose. The car can start normally and drive but it “bogs” while cruising as it runs very rich (10.0 afr’s at times)

I changed my MAF sensor and my ignition coils to new DT ones hoping for a change for the better. I also noticed that my #2 plug is “wet” with fuel, seeing as I had 1 New GDI injector already, I went ahead and replaced the gdi injector for that cylinder thinking it may be stuck open, after doing all of that I still have the same symptoms. :sigh:

Right now I am stuck and need you guys help

My car is fully built and turbocharged. I’ve driven my car around on this tune for about two years without issues, I spoke with my tuner and it is nothing easy for him to diagnose, he says if he had to guess, judging from the logs that it looks like something was changed, which isn’t the case, so I’m just trying to find the issue here.

Any suggestions? :wub:

Is your long term fuel trim +25/+30? because overall fuel time is STFT + LTFT.


If you changed the injector and the MAF sensor it might have different flow characteristics. So adjusting the tune might be the solution.


The only other thing I can think of is maybe your turbo is worn out. Can you freely spin it with your hand? it might be time for a rebuild.



Would you be kind to supply a datazap.me log it would help out alot.

here is a log with a WOT and a cruise with a small WOT, stopped midway through WOT because it started miss firing.

what would be causing my RPMS to be fluctuating like that?

https://datazap.me/u/kris86/wot?log=0&data=31

https://datazap.me/u/kris86/cruise-wot?log=0&data=31

this one is me at a stand still free revving

https://datazap.me/u/kris86/free-revving?log=0&data=31

The issue seems to be very intermittent, does not happen all the time. While going WOT the car started to miss fire in the higher rpms in one of the logs so I back off early through the pull

@steve99

would you have any assumptions?

Bump

Check the DI computer on side of motor has all mount bolts thrre of them installed and tight especially the lower hard to get one they provide ground to the di box.


if thats ok could be leaking injectors


log some idle when car warm no throttle jist let it idle and log for say 3 or four minutes

just back checked that the ECU is properly secured.

so went ahead and did the idle log before going to work for you

https://datazap.me/u/kris86/5min-idle?log=0&data=31

Also did another revving at stand still, you can see how rich it get every time I stab the throttle.

https://datazap.me/u/kris86/free-rev?log=0&data=31


your help is GREATLY appreciated.

Oh wait. Just realized you asked for a warm idle, my bad. I’ll do that when I go home for lunch

manifold pressure is fine doesnt look like leaks
if you have already cleaned replaced maf then it looks like its could be aDI issue likely injectors leaking damaged seals


if it going rich amd high negitive trims means its over fueling


infortunatly you canmot rearly confirm leaking injectors from logs so its my best guess as other things look ok


it could possibly be leaking port injectors they are easier to get to so maybe check those first.


but DI seals are known issue

Thanks for taking the time out your day to assist. I’m going to go ahead with changing the port injectors and then see what happens from there, if nothing at that point then I’ll change the remaining three GDI injectors

Much respects again steve, always giving a helping hand

So I went ahead and installed some new identical injectors, but still having the same issue.

I’ve already recently replaced the following trying to find this issue :

New DT Ignition coils
New DW 900cc injectors
New o2 sensors
1 new GDI injector ( on plug that looked wet with fuel, others were ok)

I’ve done a compression test and a smoke leak test, all is well.

Any other suggestions?

Check maf sensor is not dirty or oily, clean maf sensor. If runog speed density tune also check MaP sensor is reading correctly, should read 1 bar with engine off and ignition on
if runnog flex fuel check flex guage reading is same as that logged in ecutek