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Idle drops low and dies when car warms up

The car runs just fine when I start it up. Idle is nice and stable, no idle surge or anything.

Once it warms up the idle will be normal and then just fall on it's face. The ECU tries to save it and sometimes does but sometimes it can't.

I suspect this is a closed loop situation. Looks like it is running rich (black smoke from the tailpipe) and my wideband reads 10-11:1 when this is happening. If I give it some gas, and hold it at part throttle at say 4k rpm I get 14.7:1.

My Innovate LC-1 wideband is in the stock location. It is also setup to simulate an analog output.

I suspect that the wideband has gone bad but not sure. Runs perfect until it warms up. No idle surge BS. Vacuum is nice around 21hg.

I just got done with a turbo swap and noticed this problem started right before I replaced the turbo.

Thoughts? /ubbthreads/images/graemlins/dunno.gif

Last edited by a moderator:


Well-known member
Jun 19, 2011
I cant quite remember where I read this, but I think it has to do with a temp sensor for the ECU on the water neck or the FIAV.


Well-known member
Mar 28, 2012
colorado springs, colorado
What are you using for engine management? Thats pig rich, for sure. Even more rich than id think necessary or normal for warm up.

Tuner Pro...have been running the same tune for years though and the tune is not set for anything richer than stoich at idle.

Looks like 2 plug wires were loose....gave it some gas and 2 of them popped off.
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