Idle Rock Solid except when hot and putting it in park

[bennydee82]

My engine idle drops considerably when I put it in park or neutral after it's warm. It will drop down to 200-300 rpm for a few brief seconds and 50% of the time the engine stalls. The other 50% of the time it 'recovers' after some sputtering and stabilizes at 500-600 rpm. It is only when the engine is warm, and it only happens immediately after I put the car in Park or Neutral. When the engine is cold, I can put the car in reverse or drive, then put it right back in Park and the RPMs hold rock solid, no wavering.

At no other time do I have a problem with idle. On engine start, the RPMs are steady, whether the engine is cold or warm. The warm up Tach schedule (I'm making that phrase up because I don't know what to call it) is just what it should be, starting and holding at 1300-1400 rpm and then dropping down to 1000 rpm until I put it in gear. Reverse idle is fine. Idle in Drive is fine.

I checked the IAC and it's clean. Anyone have ideas?

 

[aldive]

Have you checked the IAC?

 

[dogfriend]

.

I checked the IAC and it's clean. Anyone have ideas?

Its not a clean or dirty thing. My first IAC failed this way - it worked fine when cold, but when the engine was warm, it would idle very low and stall if you put it in R or D. If you feather the gas a little, you could keep it running enough to get going, then it would work fine until the next time.

What was happening: The internal spool valve inside the IAC was sticking closed. This would only happen when it was warm - probably because the valve expanded at a different rate than the outer housing. On my IAC, I could see a shiny area where it was rubbing on the internal spool valve after I removed the IAC.

 

[bennydee82]

I

 

[bennydee82]

What was happening: The internal spool valve inside the IAC was sticking closed. This would only happen when it was warm - probably because the valve expanded at a different rate than the outer housing. On my IAC, I could see a shiny area where it was rubbing on the internal spool valve after I removed the IAC.

I don't see anything shiny. I tried moving the valve and it wouldn't budge. Should I be able to move it?

 

[dogfriend]

Its been a long time, but my recollection is that you should be able to move it pretty easily.