Hey everybody. i was hoping i could get some help on figuring out why my truck is acting funny. I have a 99 dodge dakota sport with the 318 in it. Well when i start it up sometimes it will rev high and then lower and then rev back up and do that a few times and then be ok. then i go down the road and when its still cold its not too bad but when it warms up, every little bump i hit in the road and the rpms raise up a bit and then drop back and it just does it over and over and drives me crazy. at first i thought it was the tranny slipping but i can take it out of over drive and it still does it and it doesnt do it at all on acceleration. it only does it when i am running down the road at a constant speed. it doesnt shift funny or hard or anything. any ideas before i go out and spend a ton of money? thanks alot!

 

Sounds like your IDLE CONTROL MOTOR, i had to replace that on my 98 Ram. It would search for a idle speed by fluxating up n down.