1994 F150 5.0: Ok so I've been dealing with this for awhile and it's starting to drive me nuts. Whenever I start my truck the engine rpms drop really low (almost to stalling) then return to normal. This sometimes happenes once and sometimes up to 5 times. When it surges low the battery gauge drop really low too. After surging a couple times the truck runs fine. No check engine light, nothing. I've checked all the fluids and checked the alternator with a battery tester and that seems to be working properly. This rarely happens when the trucj is stone cold and does its fast "warm up idle" But if I turn it off and then start it up after it's a little warm then it always surges.

 

This is somewhat of a wag, as there are other things that might cause this too. But I suspect the timing chain in cases of wandering idle, as you describe your case.

Pull the distributor cap. Rotate the engine by hand until the rotor moves. Reverse the rotation of the engine, and note how far you have to turn the crank before the rotor moves. More than 5 degress could be your issue. 10-15 degrees you should replace it ASAP.

 

It was simpler than I thought. I just swapped out the Idle Air Control Valve. Problem solved.