Recently, I changed my entire map back to stock and went for a long distance trip. (I did not want to use the untested map and lug along my laptop).

Made some max speed run during the trip and everything went well without any hiccups.

Upon my return, I flashed back my latest tune and the car starts to stutter during idle and lean out a lot when I drive it (in city).

Any idea why ?

Something must have happened during the trip, O2 sensor getting insensitive, injector failing (thus the leaning), etc ?

Any advise from you experts will be greatly appreciated !

 

is your car an VIII or IX ?

 

If it's an untested map...I would think to start with that?

 

Is it just at start up or is it all the time when you're driving in the city?

Is the weather the same or has it changed? Maybe it got colder and thats affecting the warmup period.

 

Evo 9's reset their fuel trims during every reflash I believe so maybe its your fuel trims are off a bit and you need to wait for the ECU to make the appropriate corrections? All depending on whether you have an 8 or a 9 of course.

 

I'm driving Airtrek (EVO7-based), and weather condition before and after are pretty much the same.

When I said, "untested map", basically I had not completed all range of tuning and do not want to bring this "working in progress" map along.

Strange thing is, I noticed the AFR starts to lean out dramatically even by simply adjusting the fuel map by 0.2 to 0.3 ! It used to take a lot more to see significant changes. (Note: I'm running open loop).

Which makes me wonder if the fuel delivery system or the o2 sensor/cat are "aging" ??

Gave up on adjusting the fuel map, since any minor tweak causes lots of leaning out. I revert back to stock fuel map, switch back to closed loop and now re-tweak the timing. Very strange indeed,

 

That is why i asked... if it is an VIII, he needs to reset his ECU and drive again for awhile to allow the trims to settle down. With a IX, the reflash alone should have done that, but he still needs to drive a bit to allow the trims to relax, if... it was that big of a change.

OP... I'd imagine you changed something else in the tune that you maybe missed, or just need to a lot of driving to allow the car to settle. Jump on the highway for 20 minutes. You didnt mention swapping any parts out so i dont think that is it. Id go thru and check all of your coupler connections.... maybe the trip jarred something loose

 

Open loop can be finiky because it has no 'memory' like closed loop offers. Just jumping thru the fuel/load cells can cause irregular fuel changes to happen quite drastically at times.

 

Thanks for all the feedback, I'll let it run closed loop for a while and slowly lean out. Hopefully it responses to the minor tweak rather than a drastic one