idling problem

[scott hunter]

i have a 2000 21v. i went out yesterday and the motor was idling fast at times. it normally idles at 700 rpms, but a few times it would go up to 2000 and stay there until i shut the motor off. sometimes it would go back to 700 rpms and sometimes it would vary any in between 700 and 2000. i have the 350 mag mpi motor. i took the breather off and looked around it's all electronic, no idler adjustment screw. anyone have an idea on whats going on

[Tige M.D.]

have a shop check the idle air control valve (iac).

[Tahoe32]

Do you notice your engine revving like it is at 2000 rpms. My rpms will fluctuate sometimes but the motor is not revving like it is. I found out my tach was the problem (false readings). I could tap my tach and it would return to the 600 rpm idle speed. I replaced the tach it it is fine now. I have the have the 350 mag with 315 hp.