Rough idle

[OldRedFord]

I have a 2002 Ranger with the 4.0. The engine wont idle for crap. If im at a stop sign or red light I have to rev the engine to around 1000 rpm's to get it to not stall. The idle speed jumps around irradicly, sometimes the truck stalls out. There also sounds like there is a slight miss in the ignition. I have cleaned out the IAC. There is no check engine light on. Ive taken it to the dealer, they had it for 2 days and I took the truck back, they hadnt found the problem in that time.

 

[97RangerXLT]

Check the egr valve assembly. I have had this part rust out and leak exhaust, and when it does, the truck runs just as you describe it. This has happened twice, once at roughly 50,000 miles and again at 105,000 miles.

AJ

 

[Earl43P]

Disconnect the IAC connector while it is idling shittay.

If it idles the same = bad IAC.

Clean your MAF, pull, clean and gap your plugs (or replace) and test your wires (or replace).

Do your heat/ac controls work ok? If it's defaulting to defrost under acceleration, you have a vacuum leak.