Cold weather idle

Ok, I'll try posting in here.

First - 2002 Cavalier, 2.2L OHV, 60k miles
New - plugs (single platinums I believe at 50k), wires, fuel filter, air filter

About 2 months ago, when the cold weather hit, I started having a strange problem at idle. The car normally idles at about 650-700 when warm, about 1000 while it's still cold. Well it started sticking at 1000 even after it warmed up. This never happened in warmer weather, only very cold. Sometimes hitting the throttle pretty good would return the idle to normal after it warmed up, but most of the time I have to turn the car off and restart it after it's warm. That always fixes the problem.

The idle does not surge, is not rough, and there's no loss of power or hesitation. There's no knocking, misfiring, stalling, etc. It just idles high. There hasn't been a significant change in fuel economy.

On a weird side note, my car, my g/f's car, and a buddy's car all got worse than usual gas mileage over the last two weeks...formulation change?

Last week I tried cleaning out the throttle body like the Haynes manual suggested with a little carb cleaner around the throttle plate, and sprayed some into the IAC port. I didn't take the IAC off cause the idle wasn't rough and it's crammed agianst the firewall pretty good, and I didn't feel like removing the throttle body. A GM guy suggested some Chevron Fuel System Cleaner. Tried it, no difference.

There's no check engine light either. Suggestions? ECM maybe?

Thanks.

Erik

Depending on where you are from, that is normal. In places like Michigan, winter gas and cold cold air is to be attributed to both of those problems.

if nothing else is affected then i wouldnt really worry, if it gets worse i would suspect an iac. otherwise i would peek around for vacuum leaks, sounds like its a pretty small one.

I'm probably discounting any problems with the IAC or vacuum leaks, since once it goes back to normal (restart the car for example) there's no problem any more.

If it were one of those two things, I would expect the problem to be reoccurring in any weather condition.

I think I'll blame this one the extreme cold and winter gas as suggested above (especially since I've had no problems the last 2 weeks since the weather has been a tad more mild). Thanks!!