idles fast, then slow, back and forth

[Chuck Willis]

When I cold start my 86 2.9 v6, the motor fires right up, idles at 900-1000rpm for a couple of seconds, then drops to 400 rpm, almost dies, then back up to 1000 rpm. It bounces back and forth between 400 and 1000 rpm, over and over at about two second intervals until it warms up. Once the motor warms up, it idles perfectly.

A couple of ranger station experts actually helped me get this truck running, 'cause I was lost in space. When I first got it running, it idled perfect on a cold start. This fast/slow/fast/slow idling started happening a week or two after I got it going.

Any help or ideas would be excellent.

thanks, Chuck Willis

 

[adsm08]

Go get carb cleaner or gum cutter and spray out the idle valve until it starts coming out clear.

 

[Chuck Willis]

Thanks adsm08, I'll try that out.