Excessivly high idle & loping

'98 with 3.4 SFI idles@ approx. 2500-3000 rpm. Lopes fast when cold, slows loping speed when warms up. Also pumps air into cooling system from moment of start until shut-down.
I realize this is probably a combo of causes for each problem.
This is a set none at the shop have come across previously. That high of idle speed is puzzling the most.
Any suggestions would be extremely appreciated.
No stuck throttle linkage, & no codes shown when scanned. Realize air in cooling sys. possibly from head gasket leak.

What do you mean "Also pumps air into cooling system from moment of start until shut-down"?

It sounds as if you are describing bad head gaskets. If that is the case, high idle is the least of your troubles. Heads may be cracked or just leaking gaskets. If it has been driven any amount with leaking head gaskets, cam bearings may also be bad.

I'm in the process of replacing the engine on my '02 Silhouette with 140,000 miles due to head gaskets/cam bearing issues.

Sorry for so long getting back. Already told them about head gaskets. Found high idle & lope cause more by accident, shorting cruise control, activating no load rpm limiter in system.

High idle is generaly a vacuum leak or the IAC is dirty or bad.

:2cents:

rookie here:

My 03 olds sil also has very high idle issues, sometimes right when you start it up. not sure how to check a vacuum leak, and I dont know what the IAC is. Any tips on what I should check out first?

Thanks