I recently discovered something strange about my Sunfire. Whenever the weather outside is cold the RPMs will stay at about 1200 when the engine is cold at idle. However, once the engine warms up, the RPMs will stay at just over 1000 at idle. If I turn off the engine when it's warm and start it again right away, the RPM will fall to 600. Now this has happened at least twice in the past winter. At first I thought nothing of it and it never happens in the summer. What's going on? I have the 2.2L with 3 spd auto. It happened today too but it wasn't all that cold outside.

Normal? High Idle when your engine is cold, low when it is warm.....

I adjusted a carb on a 91 Jeep Wrangler and this was the case. I had no clue what i was doing....but thats the only concept I grasped.

That's the problem: when the engine warms up, even after half an hour of driving, it stays at just over 1000 rpms at idle. However, if you pull over and turn off the engine and then start it again right away, the rpms will go down to 600. And this seems to happen only in the winter. I just don't know why when you turn off the engine the rpms fall to normal when the engine is warm.

check vacuum lines.

Is it a stick?

My Cav Idles at 1100 but it dips to 600 sometimes.

Robby002: All vaacuum lines are ok, no leaks.

Mark: It's a 3 spd auto. And yeah it dips to 600 rpms if you turn the engine off and start it again. And this happens only in cold weather.

Someone suggested it may be the harmonic balancer, does this engine even has one?

Isn't 600 Normal in an Auto? The high Idle may be the problem.

i do know the idle in cars are supposed to be high in cold weather, but only for a short period of time to get the engine up to temp. you say vacuum lines are ok? maybe it might have something to do with your throttle position sensor. im not too sure but it could be a possiblity. unless for some weird reason your PCM is telling your car to stay at i higher idle. hmm that is sorta weird to me.


Silly ricer, useless wings are for penguins.

AFAIK 600 is normal in an auto
the 1200 idle is to get the cold engine up to proper heat.

when it's at 1000 rpm, is it in Drive or Park?
when it's at 600 is it in Drive or Park?

Just asking, b/c when you turn ON/OFF it needs to be in park, and i doubt you putting it in park when you're idling at a light....
maybe that's why?

Willem: it happens when the car is in drive or park. If I put it into park, shut off the engine, and start it again right away the rpms will go down to 600. I know 600 is normal when the engine is warm. However, what I don't understand is exactly what Matt&Marissa said: if the engine warms up, why won't the rpms go down to 600 instead of 1200? Why does it require me to restart the engine for the rpms to go down to normal idle when the engine is warm. That's my issue. The fact that when the engine does warm up, the rpms will not come down below 1000 unless you restart the engine. But bear in mind this happens only occasionally and only in the winter. It didn't happened once during the summer.

because the computer is cold when you first start your car
I do not know

oops sorry lol. its supposed to idle around 1200rpm at a cold start i just dont understand why it only goes back down to 1000rpm istead of normal 600rpm idle when your car warms up. but will go to your normail idle when you shut the car off and restart it. that confuses me. thats the only reason i could possibly say it might be your throttle body position sensor. normally i see stuff like "i have high idle all the time even when i restart the car."


Silly ricer, useless wings are for penguins.

Isn't there a sensor that controls the RPM's during this time of fast idle?

When the engine is turned on first thing in the morning (assuming there is a sensor) it's activated, but shortly after - before reaching operating temperature is seizes to work properly. After shutting the engine of it resets and recognizes that it has reach operating temperature and the RPM's settle to normal.

Note: theory only