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Hey guys, i'm hoping someone on here can give me a direction or tell me what I am missing here.

I have a pretty mild ls1 swapped car and i'm having a little trouble with the idle control. The engine idles really happy and hits the target 95% of the time, the issue I am running into is when I am decelerating and using the engine to slow the car down the STIT start to wind up in the negative direction (I understand that it is trying to reach the idle target and the adaptations are pulling airflow). So when I finally clutch in and come to a stop the STIT are so negative that it chokes out the engine and causes to engine to stall or come really close to stalling.

I have tried to modify idle airflow tables to restrict the amount of negative idle trim but nothing I do seems to alleviate the issue. I'm sure I am missing something or don't understand how some of the tables function. (just going off of the short description hp tuners gives)

Has anyone come across this before or know what I am missing? I'm quite familiar with standalone tuning, I'm just starting to get more involved with hp tuners so any advise is greatly appreciated. I've linked a log of the condition as well as my .cal file.

Thanks everyone!

Attached Files

Do you have a VSS (Vehicle Speed Sensor) connected to the ECU? I would expect an OEM ECU would use that to prevent idle control from activating if the vehicle is moving. if you don't have that hooked up, then the ECU is blind as to the actual operating condition.

If you can't fix it in the ECU tuning, you could just blip the throttle when clutching in, so that you exit the idle control and start fresh.

Hey David, thanks for the response. Yes I have a working and properly calibrated speed sensor to the ecu. The throttle blip doesn't really work for two reasons. First being that when I blip the throttle it doesn't clear out the STIT, it actually takes a little bit to clear out. Do you know if there is a way for that to update faster? The other issue with the blip is that it really is only a problem right as i'm coming to a stop so me not being a forklift operator I use my right foot for the brake so that doesn't really work. Thank you for the input however, I appreciate it. I'm hoping there is someone here that knows how the factory dealt with this. Maybe what i need to do is add airflow mechanically with the idle screw so the engine can't choke itself all the way out, then just re-calibrate the idle valve. Maybe that is how it's supposed to work from the factory so if the idle valve fails it will still idle?

Thanks again, i'll post up my solution either way.

Perhaps this thread will help you:


There is useful info about the idle control in posts #6 - #8

I see mention of a minimum speed required for the adaptive idle to become active -- is there a parameter to set what that value is? Also, I wonder if the ECU is looking for a clutch signal - and could think the clutch is disengaged so it should be doing idle control.

I think you probably need to try decreasing your Base Running Air Flow as that will interact with the STIT, according to several threads I read on the HP Tuners forum (I just searched HPTuners and STIT).

BTW -- try closing the idle screw so that it will open the bypass air to control the idle. If you have the throttle too open, then the bypass air can't do it's job.

Thanks David, I'll go check that out.

As of right now I have the idle screw closed pretty far. It basically relies on the bypass air to even idle at the moment. I'll go take a look at the link you posted.

Thanks again!

Just wanted to follow up with the resolution to the issue. I had the idle adapt disable speed set too high... I just didn't realize it because it's under the throttle cracker tab. After reading the brief description when hovering over the tab it all made sense. I hope this will be useful to someone!