markrushton

Does this sound like a bad Idle Stabilizer Valve? I start up fine. 30 mile drive to work down the highway. By the time I get to work or back to home, the idle is roaming in the 1600 to 2000 rpm range, is running rich, mileage and acceleration are compromised. If I adjust the air/fuel mixture partway through my trip then the next time I start up the idle is way too low (400 instead of 1050 or 1100). Otherwise, car runs great.

Onward

Bad coolant temp sensor? Mine corroded and gave similar symptoms.

Whitjr

Adjusting the mix is very delicate, I wouldn't do that too many times w/o returning to the right setting...

markrushton

Had the O2 sensor, full tune-up, and cat converter replaced about 2-3 months ago. After all this is when the situation became pronounced, although intermittant.

Sometimes I can go for 4-5 days without problems. Other times it is daily.

I think the key here is that it is usually fine on start, but once the engine is warmed up (12-15 miles on the highway) is when the symptoms appear (high idle). It always disappears after the car cools down.

markrushton

I had the coolant temp sensors checked out a couple months ago, following the major tuneup, O2 sensor and cat converter replacement. All checked out fine. There are something like 4 or 5 of those coolant temp sensors if I'm not mistaken, at least on my 1984 4000S.