Hi,

I have problem with hesitation idle and even stalling after I do reflash or just clear trouble codes and reset ECU (using Cobb AP). Usually next day the problem is gone.

It looks like the ECU learns some parameters and then the problem is solved. I wonder what could it be - they are not LTFTs, as these are lerned a while after reset but the problem with idle remains.

Does anyone know?

 

do you have upgraded injectors? It takes about 10-20 minutes for the LTFT's to be figured out.

What about your MAF housing? Do you have a bigger one?

 

Everything is stock (except TBE), LTFTs are lerned after a few minutes (I see it on gauge), but stable idle only after a few hours of driving.

What the hell does it learn???

 

What tune do you have? Some of the stock maps have issues with the idle.

 

I use modified Cobb st. 2 93 oct map, but this is not map issue, as it works fine after 2 days of driving after reflash....after learning something...

 

Have you contacted Cobb?

How cold is it there right now?

 

The car has to learn to idle. It seems to go through a learning procedure every time you flash. The farther out of trim your idle is, the longer it takes to get it right. I would look for intake leaks, and vacuum leaks as well in all the usual places.

 

Your car has fuzzy logic ...... every time you reflash it has to understand whats going on and adjust its mapping to compensate. the longer it sees input the smarter it gets.

 

This helps the car run better in drastic temp differentation, and altitude. but it hinders performance when there is a boost leak or vaccum leak, because the ecu will try to compensate for the problem.

 

Well, i guess this is not a compensation for Vacuum leak. The LTFT idle (0-6%) is learned afrer a few minutes of idleing and stay the same.

But the hesitation and stalling is only corrected after a few HOURS of driving. So it is something different from LTFTs for sure.

 

There are 4 fuel trims.

1 is STFT (short term, it's what idling fixes).
1 is LTFT cruise, this is what a long time driving adjusts
1 is LTFT idle, long time driving adjusts this as well
1 is LTFT (something else) and it's not used (well it is if you tell it to be, see the LTFT disable for WOT thread)

Your injector scaling and latency will impact all of these. I'm betting that your LTFT idle is out of whack until you drive for a while. Log that.

I'm not sure what the AP calls all these though.

 

As written above, I logged all of these, the LTFT is LEARNED a long time (hours) before the idle works fine. I have no idea why...

 

which LTFT?

My LTFT Cruise and Idle change pretty much like clockwork every 4 minutes depending on how I'm driving.

 

Ltft idle is leaarned after a few minutes of idling in garage after reflash, LTFT Cruise is learned after few minutes of light driving.

However both LTFT are in -2 to + 6%, so they do not influence the injection timing much.