Interesting engine problem

[tsiawdspeed]

This is about a 1996 TSi AWD. For some reason, my car will not idle when warm. When the car is cold, it idles perfectly but when the car is warm, the engine dies just like if I would turn the key off as soon as I take my foot off the gas. There are no CEL's and the car acts completely normal when I don't take my foot off the gas and at near-idle RPM when I have my foot on the gas slightly. I am thinking maybe the idle air speed valve or the throttle position sensor are broken. Any tips?

[blageo23]

I Was thinking those too but also maybe check for a vacuum leak. Maybe something expands when it get hot.

[tsiawdspeed]

I checked most of the vacuum lines I could see and they were all connected and not cracked. If it was a vacuum leak, wouldn't it most likely affect engine performance all the time instead of just when trying to idle?

[tim]

If you have a massive vacuum leak you will suffer idle problems too. Try unplugging the brake booster when the engine is running and you will see what I mean.

[slowbubblecar]

I would replace the 0-ring in the BISS first as it is probably 10 years old and has never been replaced.

[Bunta]

This is very Noobie of me but back then when i had my 240 with the hks bov, when i down shifted and then went to neutral or something to that extent the car would just automatically die.

[TheBlizzard]

Try adjusting your BISS screw a bit to see if that helps. If you adjust it and it still dies then check for leaks. Sometimes idle problems can be tough to diagnose, it could be anything right down to your coolant temp sensor.

[tsiawdspeed]

This idle problem is hard to diagnose because when it is acting up, it will not idle. It just shuts off. It doesnt stumble or idle rough for a little bit, it litterally just does not run. Very strange to me. I am gonna take the idle air controller off today and see if anything is visibly wrong with it. Any other suggestions?

[Berda]

bov vented to atmosphere or system?

[tsiawdspeed]

BOV is a 1g routed into the intake

[tsiawdspeed]

Just went out to work on the car a bit and I started it up and now it wont even idle when cold. So I ran it for a bit while holding the gas down slightly. A few things I noticed through the pocketlogger:

When the car was not running, I was seeing a slight airflow (.16 lb/min) not sure if this means anything
After the car was almost warmed up, the idle was fluctuating about 50 rpm, which was noticible
The coolent temperature sensor and TPS were all giving normal readings