Hi all,

I've been tuning my idle recently and got it to a pretty reasonable place. While pulling off the highway, I coasted down and pushed in the clutch, and the engine died. No changes were made to the idle settings and the car idled hundreds of times perfectly before and after this incident.

Looking at the logs, it seems like the idle valve did not open as early as usual, and took longer to open than usual. From looking at previous logs (and the end of the provided log) the IAC valve opens while the engine is coasting down, so that it is ready to "catch" it once the clutch is pushed in. I don't understand why the IAC valve was: A) not already open the proper amount, B) Took significantly longer to open the proper amount.

Is there a setting that controls the conditions for when and how quickly the IAC valve opens? I looked in tuner studio but can't find any such setting. Maybe I am just missing something simple.


Any insight you all can provide would be greatly appreciated. Thank you.

P.S. If you are going to open the log in a viewer, the incident I am talking about happens towards the end of the log. You will see a coast down followed by engine stall.

 

It doesn't actually need to close at all. There's a setting I can't recall where.

 

I found what I was looking for. I had the minimum MAP to enter closed loop set too low. So when coasting for too long, I would be in closed loop and the IAC valve would be gradually closing trying to bring down the idle.

I set the min value to 26kpa and it seems to be working well now.

 

I had a similar issue; it seemed much worse when the car was heat soaked especially after long drives on the highway. RPM would drop very rapidly when clutch was pressed, and sometimes overshoot target idle RPM. Only a couple of times did it actually stall.

I noticed a few things that were off in my tunr that I had to address. One was taking a more methodical approach of setting idle valve initial values, as well as playing with my general closed loop idle settings like ramp to set point.

The bigger thing that I think was the root cause to my problem was the engine thought it was going in to overrun and this would sometimes (but not always) cut fuel. It wasn't consistent so I was scratching my head for a while on that one.

Anyway, I played around a bit more with engine states and overrun settings, both of which I originally picked somewhat arbitrary numbers for and/or just uses base map values. Tweaking these helped immensely.

May not be related to your issue, but thought I'd share as you have similar symptoms that others might run into. Check your engine states settings, and make sure they make sense for your setup.