Short term fuel trims max out, car keeps going lean randomly. Chrome ECU tune attchd.

[vr4whore]

Car runs/drives perfect at WOT, but when I feather the gas while coasting I feel bucking. and hesitation, sometimes while driving my AF would jump to 16-20, it will NOT stall, then it would fix itself and I would continue driving. Sometimes while sitting at a red light it will also go super lean 16-22 and the car will NOT stall.

Looking at the logs we figured the short term fuel trims would keep adjusting and eventually max out at 12. I attached my main tune if someone can take a look at it.

I have tried the following:

New factory o2 sensor, no help
New wideband sensor hooked up as a narrowband to the ECU, no change.

[Jesters Deadd]

When your low fuel trims max out the ecu will reset and try to trim your fuel again. That is why you are getting the random jumps to lean while driving around in closed loop with max fuel trims.

Did you add fuel in the low fuel trim range?
What are your mods?
Have you tuned your car at all?
I always setup idle and cruise first when I tune a car.

[Unlogic]

Also check for exhaust leaks. A small leak will affect low trims but may not be noticeable at all when it comes to mid and high trims due to the larger amount of exhaust flow.

[vr4whore]

Hey Adam, this is Roman from Calgary Canada.

We just hooked up the wideband as a narrowband to see if it makes a difference, and it didn't

I still have the old tune loaded.

Any suggestions ?

Thanks!

[vr4whore]

That's interesting, is there any other values in evoscan that will give away an exhaust leak ?

[dyter]

I think injectors lag is bad