Sorry I popped in late on this one.

This is normal behavior in cold weather. The PCM is commanding the cold idle to maintain that RPM until warmup is complete.

If you want proof of it, hook up a scantool and look at the 'idle req rpm'. If it'* the same as the indicated rpms on the scantool and tach, you're golden.

Again, this is NORMAL intended behavior in cold starts. Your cars don't have problems. Mine does it too if it'* cold enough, as does nearly every other car here.

MUSTAFA has spoken.. guess all is good then..

I'm bummed that so many parts have been changed to solve this. But it'* not a waste. There'* some comfort in knowing all that stuff is new.

Bill..

I'm still a little confused... I understand that the PCM is calling for a higher idle, BUT why doesn't it automatically come down? From what I understand (and have witnessed in 100s of other cars) it should. My car will run at exactly 1500 RPMS forever if I let it(longest I've let it go is 30 minutes...temp guage was right at 195). :?

I've never let mine run long enough at idle to see when it comes down if it does at all. We've actually discussed this topic before a couple times on this forum and beat it to death. Nearly every car here, properly tuned, will act the same way by design.

The reason it'* not a timed function may be that GM didn't expect your car to sit at idle for 10 minutes in the morning. They expect someone to drive it before that time has passed.

I know for a fact that mine will high-idle for at least 10 minutes on a cold morning until I tap the throttle. The only people that can answer this question are the GM design engineers, and most of those that participated in the Bonneville PCM design are probably retired, or don't remember.

Mine goes down automatically

Once the temp gauge starts moving a little past 100 [when I did this, my temp gauge was very inaccurate, so I don't know what it would be in actual temps], then the idle would decrease, jump up for 10-15 seconds, then pop down, and would stay there. Guess my car is so dumb.. it'* actually smarter than yours .


-justin

Don't be bummed about the parts I put in.
I had an extra IAC from the bone yard so I tried swapping them. Then changed it back. Likewise with the temp sensor. I swaped them back and took the new one back to the store.
The upper intake and gaskets were actually done as preventative maint. and to resolve a small throttle body coolant leak.
If I understand you guys correctly all your cars will hang @ 1500 rpm when started below 45 deg. Like vitals and mine and will not come down regardless of time running or temp unless you kick your pedal??
It appears opensouceguys car works the way I think my car should......

Your assumptions are correct. In Opensource'* case, the 87-91 ECM (as opposed to PCM) is less controlling.

Yupidy yup. My ECU knows very little about the engine, and what is all going on. Although your'* should function this way, it won't, because of what Bill mentioned, in that my ECU is much less controlling. I don't see why GM ever upgraded from the old school OBDI electronics, it seems I am having the least amount of issues, out of all the 92+ers.


-justin

My 90 SSE acts just like yours. I could start it go in the house and it will
automatically idle down to 700 rpm by itself.
I guess cars are getting less intelligent or the engineers are.