Why would your 99 Ford Ranger 5 speed repetitivly rev up to 3000 rpms while you are idling at a stop light with your foot off the gas and then suddenly drop back down to normal?

Might have something to do with the timeing. I have a 1991 ranger that would drop down to 500 RMP from 1.5K when idleing before i lost my timeing.

Answer

replace tps ford had a tsb about this

sorry to complicate things, i have had my ranger for 4 years 3/12 of which have been speant trying to figure out something similar, it only happens in warm weather, usually at high altitudes it does not do it, it only gets worse. i have run into only a couple people on-line to have the same problem. i have change tps iac and just replaced mass air flow sensor, only have 20 miles with it on but hopefully that was the ticket.

it could be the air flow silinoid remove the silinoid and clog the hole with your finger and see if it idels down . its located by the tps

I had the same problem with my 2000 Ford Ranger revving to about 3000 rpm for no reason and then dropping back down to normal. The problem was the idle air control valve was bad. You can get a new one at any autoparts store for about $50 and that completely fixed the problem. In fact it actually runs better now and idles at a lower rpm.