i bought this ranger about a month ago and everything i have done still dont fix the prob, it will idle fine then about 5mins or so the idle drops and misses and runs rough but if i hit the gas it dont have a miss at all and runs smooth until i let off the gas again. Ive changed spark plugs, wires idle air control sensor? there is no vacume leaks either i already checked, Ive noticed when i unplug the front coil pack it runs rough even sounds like a miss i plug it back in and it runs alittle better but when i unplug the back coil pack it just drops idle alttle bit no big difference so im wondering if my back coil pack is bad. i have good compression did a fuel pressure test it passed it even alittle high but normal, new air filter cleaned the maf, im just stomped by what it could be.

 

Not sure if I can help, but I'll give it a shot since no one else has tried. Sounds like you did all the things I would have. Your post was not clear on the Idle Air Control. Did you replace it? That would be my first guess. Mine had exactly the same symtoms as yours and it was the IAC. You might try cleaning the throttle and throttle body. Also check the operation of the TPS Throttle Position Sensor. If you have a Haynes Manual it tells you how to do it. Did you disconnect the battery for a while to reset the computer after doing all that work? It's worth a shot. There are so many things that can affect idle it can be hard to nail down the problem.

 

What ended up fixing your problem... I know it's been 14 years... but why not ask? Lol