While the truck sits at idle the motor will regularly rev up to around 1500 rpm then back down to about 1000 about every 3 seconds, any ideas on what could be causing this? Truck's got 170k miles if that matters.

 

one thing that has been a problem is IAC, Idle Air Controller, mounted on the side of the throttle plate , they get funky in side , just remove clean it an try it again, use like some componet cleaner spray it inside of the body of the controller several times , an spray a bit in the holes on the intake that match the controller . Another problem , usually only when its cold , is the gaskit under the upper intake they loose there sealing ability after awhile an with the engine cold before things heat an expand it will give you a rough idle on start up .

 

Ramrod48 sounds like a man of good advice. The IAC valve gets carbon buildup overtime and can easily be cleaned out w/ a non-chlorinated solvent. When the IAC valve gets too much builup inside, you might have trouble with your truck stalling out at idle speed. If not the IAC valve then it could be time to change the PCV valve (a $5 part at your local dealership).

 

Just too MANY years bent under the hood of these gal's

 

i have a 95 Ford Explorer and it has trouble idleing sometimes like when i drive it awhile and when i start it back up andlet it idle it will spit and sputter, sometimes almost die. I was wondering what could be wrong i was thinking either the EGR valve or the Idle air control like was said earlier in the post, if any i deas id like to hear them

 

sounds like idle air control..probably all carboned up