ECU reset + warm start = stall

[phrosty]

Hi guys, noticing a weird thing happening when I start the car after I reset the ECU -- disconnecting battery, flashing a tune, etc.

If the engine is warm, it'll stall out. I need to give it some revs to keep it alive, and get into gear at higher than idle revs or it'll die. Once it's in gear it's good to go.

If the engine is cold, it starts up and after the initial high RPM it dips down nice and low, not enough to sputter but enough that DRLs will dim out, and then recovers. My assumption is that the cold start routine is giving extra fuel and thus preventing the stall.

After I get it moving, lifting off the accelerator will cause a similar RPM dip as the cold start bit. Either way, after a few minutes of driving the car appears to calibrate and has no trouble starting up after that, warm or cold, and no RPM dip.

Any ideas to the cause or how to diagnose? I don't believe it to be a leak as fuel trims are spot-on, and I hear nothing out of the ordinary. It drives otherwise normally.

[humfrz]

Originally Posted by phrosty

Hi guys, noticing a weird thing happening when I start the car after I reset the ECU -- disconnecting battery, flashing a tune, etc.

If the engine is warm, it'll stall out. I need to give it some revs to keep it alive, and get into gear at higher than idle revs or it'll die. Once it's in gear it's good to go.

If the engine is cold, it starts up and after the initial high RPM it dips down nice and low, not enough to sputter but enough that DRLs will dim out, and then recovers. My assumption is that the cold start routine is giving extra fuel and thus preventing the stall.

After I get it moving, lifting off the accelerator will cause a similar RPM dip as the cold start bit. Either way, after a few minutes of driving the car appears to calibrate and has no trouble starting up after that, warm or cold, and no RPM dip.

Any ideas to the cause or how to diagnose? I don't believe it to be a leak as fuel trims are spot-on, and I hear nothing out of the ordinary. It drives otherwise normally.

First off, what do you mean by "flashing a tune, etc" .... ??

I suggest you turn the idle screw a half turn clockwise......

(yep, it used to be just that simple)

Seriously, maybe a tuner should take a look at it ..... or, drive it for a while to see it will re-learn the idle setting.


humfrz

[Eazy-V]

Originally Posted by phrosty

Hi guys, noticing a weird thing happening when I start the car after I reset the ECU -- disconnecting battery, flashing a tune, etc.

If the engine is warm, it'll stall out. I need to give it some revs to keep it alive, and get into gear at higher than idle revs or it'll die. Once it's in gear it's good to go.

If the engine is cold, it starts up and after the initial high RPM it dips down nice and low, not enough to sputter but enough that DRLs will dim out, and then recovers. My assumption is that the cold start routine is giving extra fuel and thus preventing the stall.

After I get it moving, lifting off the accelerator will cause a similar RPM dip as the cold start bit. Either way, after a few minutes of driving the car appears to calibrate and has no trouble starting up after that, warm or cold, and no RPM dip.

Any ideas to the cause or how to diagnose? I don't believe it to be a leak as fuel trims are spot-on, and I hear nothing out of the ordinary. It drives otherwise normally.

Did you ever get this resolved? I have a similar issue.

[steve99]

Check maf offset after start tables


Check ltft at idle after car as idled for 5 minutes if its high ie over 10% likely maf scaling needs work or you got some sort of exhaust or intake leak.


also look at afr at idle should be around 14.7


idle vacuum should be around -20in Hg or -9psi