Weird Problem at Startup...must rev engine '01 SC2

[dannyd123]

I have a problem that just started happening today. Not really sure what it is. Here's the symptoms (2001 SC2 Automatic):

1)Put key in, try to start it, car turns over, jumps to about 800 rpms, slowly comes down to 200 rpms and stops.

2)If I do the same as above but rev the engine, it will usually stay running and idle at about 800rpms (normal).

Sometimes I do the same as above (step 1), it starts up, goes to 800rpms, droops down a bit, maybe to 400-500 and then idles at 800.

Could this be the alternator, maybe the sparkplugs? Also just for additional info, I don't think it would be related, but about 4 months ago the differntial pin in the transmission broke off and shot out of the transmission casing, so the transmission was rebuilt at a saturn dealership. Could that have anythign to do with it?

Thanks a lot.

[Cat Fuzz]

Sounds like a bad Idle Solenoid or IAC valve.

[holdemjunkie]

could be iac, or temp sensor, the temp sensors on those like to crack