No idle after boosting

[Messerschmitt]

I`am using a LQ9 Twin turbo setup in my 72`Camino.
3 bar speed density mode and a Cable driven throttle body with integrated idle step motor.
The engine runs pretty decent and has no issues.
I can run the car for hours out of boost and the idle stabilizes nicely at every stop. If i boost it just a single
time, the idle is lost.
If i disconnect the idle stepper turn on the ignition, turn it off, connect the stepper and the idle is back - till the next boosting.
May that be a mechanical problem?

thanks for any thoughts

[5FDP]

Can you post the tune and logs of the problem?

[Messerschmitt]

Oops - my fault; i do a log as soon as the weather permits and come back...

[AutoWiz]

So the iac is basically a dumb stepper motor, right? 2 sets of coils to create a motion in steps but without any kind of sensor to report back actual positioning of the iac pintle. So when you first turn on the car the iac fully opens or seats so the ecu can know logically where it is. And from there it is a game of memory for the ecu counting steps back and forth. It is possible that if you have a worn or failed or failing iac that the positive pressure up against the pintle is making it skip teeth on it's driven gear and ultimately creating skipped steps. While your problem might very well be tuning related, this possibility fits with your described reset procedure. I would try a new iac.

[Messerschmitt]

Tried a working iac - Problem remains exactly the same;
will post my tune as soon as i`am at home.....

[jimmyblue]

Can you see any immature codes when this is happening?

When you say "idle is lost" does that mean it just flops
and dies on pedal release? What happens if you feather
it down to near-idle? This could be cracker / follower
needing refinement. What does IAC position and desired
airflow look like, in "working" and "not working" idle? Is
it asking for no air, asking but not getting, or too little
too late? Crash right away, or yo-yo and crash?

[Messerschmitt]

neues layout09.08.2016.Layout.xmlPinneberg Dyno 635HP.hplCamino Readout 03.10.16.hptneues layout09.08.2016.Layout.xmlPinneberg Dyno 635HP.hplCamino Readout 03.10.16.hpt

ok - tried to attach the last tune, dyno, and scanner configuration.

to be honest i did not checked for codes - will do tomorrow....

when i coldstart the engine it idles around 1000 rpm and than reduces rpm as coolant temp rises.
when the car Comes to stop it idles nicely i do not have to feather the throttle or anything. as soon as it has seen boost, the idle is completetly gone, you can not "help" it to idle in any way. Seems as the iac is completely closed and the throttle simply rests against the set screw.
Also i find it hard to Keep it alive either it wants to die or rev up like mad. (reason maybe the 102 mm Throttle Body)
on the dynolog it did the same as the rollers come to stop the engine wants to die...

[AutoWiz]

What is up with your stall saver table?



Those cells should be lower than the numbers above them and maybe by a few hundred rpms

[Messerschmitt]

Well, i altered the whole idle setup to near stock specs (opened a compare file for a 02 Camaro and did a copy and paste)
and voila; i`am back in the game. No idea how the stall saver numbers got where the were.
Car idles perfect - thanks for the help.....

[AutoWiz]

Good stuff