Idle jumping up and down horribly when cold HELP!

[MattB]

I started my G20 today and when I came to the first stop the revs started jumping wildly between 500 and 1500. It lasted about 10 seconds then went back to normal and did not reappear. The alternator belt on the car needs replacement, can that cause this? I am completely confused as to the cause....it doesn't do this at startup, only at the first stop.

[HeavyDuty]

Electrical bugaboos cause a multitude of problems.

I would clean my throttle body & clean or replace my EGR tube.

The IACV/AACV valve could be going bad or just overworked with a dirty throttle body.

There's a 'cold start' idle air bypass under the intake manifold that might be hanging open too long, allowing metered air to bypass the throttle body increasing rpm. They're cheap to replace.

[MattB]

Thanks. I'll have those checked out when I have the belts changed.