High idle when cold

[DRC]

Hey guys

I've been noticing lately (with the weather getting cooler) that my engine's cold idle seems on the high side (1300-1400 rpm). Once warm it's OK, around 700-800 rpm. I know there is no manual idle adjustment, but can anybody suggest what could be causing it to idle this high? The IAC is clean (I clean it often) so it's not that. Maybe the TPS is going bad?

[01bonneSC]

It runs high till the engine starts to warm up. It's normal.

[Nocrank]

Yup, normal for pretty much all GM vehicles. When you think about it, it must cause more wear on a engine, especially if it has sat for a while. One of the reasons I removed this function with tuning from my camaro.

[3800SERIESII]

Have the same prob. I posted a while ago. I changed the o2 sensor and there was no significant change besides a smother "warm" idle.

[01bonneSC]

All engine do it. It's basically like a choking for a carb'd engine.

[DRC]

I understand that any engine idles higer when cold...but that high? My previous car was an '05 Grand Am and it cold idled around 1000-1100 rpm.

[dz09x]

This is normal. Mine does the same. Once a certain temp is reached, it drops back down. First time i ever noticed it, talked to a GM mechanic and even he explained the whole thing to me on why it does it. Don't remember why anymore, but I remember that it is normal.

[theax40]

I just rev the engine a lil bit and the idle drops down right away.

[Nocrank]

This is normal. Mine does the same. Once a certain temp is reached, it drops back down. First time i ever noticed it, talked to a GM mechanic and even he explained the whole thing to me on why it does it. Don't remember why anymore, but I remember that it is normal.

I believe gm made the cars rev higher to heat the O2 sensor quicker as in older cars before heated sensors. The O2 needed to reach a certain temp. to measure properly. It was also to help bring the catalitic converter up to temp quicker as it does not really work until it reaches a certain temperature. It was basically all for emissions. In the newer cars it must mostly serve to heat up the catalyst faster as the O2's are heated. I'm sure it serves some other purpose to but that's the main one. Most cars will idle around 1500rpm's until coolant reaches a certain temp. If its a lot lower than this and no tuning has been done to the car. Then you probably have a problem with your IAC motor.

[DRC]

OK, so it is normal. Good to know...thanks guys!