jshuberg

Hey, this weekend I'm planning on looking into a few annoyance problems, one of them being an unusually high idle when cold. I have a US 84 automatic.

When started cold in park it idles at 1300-1400 RPMs for the first few minutes, and then drops down to around 900-1000 RPM. When in gear after the first few minutes it idles at around 750-800 RPM. I believe the most likely culprit is the aux air valve, but if that's not it what else might be causing the problem? My temp II sensor checks out good at around 1300Ω at 75°F and 220Ω when fully warmed up.

Aside from the high idle for the first few minutes, and that the idle does occasionally drift down slightly and immediately come back when warm (which I believe is more or less normal), the car runs great. A/F when warm is spot on.

Thanks much!

ROG100

Jeff - sounds to working correctly - once the engine warms up what idle do you have?

jshuberg

When it's fully warmed up it idles at around 900-1000 RPM in park, and around 750-800 in gear. Pretty much the same as when cold after the first few minutes has passed.

jshuberg

I guess I'm making a presumption here - is idling at 1300-1400 RPM for the first few minutes normal when everything else is running properly? This seems unnecessarily high to me...

ROG100

It may be a tad high if we can trust the accuracy of the rev counter.
On a cold start the engine should rev higher as more air and fuel is put into the plenum.
As it only stays there for a few what is the issue? That is what is supposed to happen after the auxiliary air valve closes and the cold start injector shuts off.
I think the revs should be maybe 650/750 at warm idle.

jshuberg

It's not really an issue, just kind of an annoyance really. All the same the plan is to tinker with it a bit this weekend and try to bring it down slightly. I suspect the aux air valve may be letting in too much air before it warms up and fully closes.