94 ranger high idle

[lew94]

I have a 94 ranger w/4.0l V6 195,000 miles idles high in park once at temp checked IAC valve reading 11omhs what else should I check could it be the vacuum modulator is bad any help would be appreciated

 

[bhawk]

We had the high idle issue for a couple years before I finally tracked it down on our 94 ranger 4.0. We tried the usual first--changing out the Idle Air Control, to no avail. Eventually I pulled all spark plugs and found them burning almost white, meaning lean mixture. That pointed to lower intake manifold leaking. So I changed the upper and lower intake manifold gaskets, and the valve cover gaskets get done while you are there, and voila, low idle, nicer startup, runs like a top now. We used to use some oil and couldn't figure out where the oil was going as it didn't smoke, no black on spark plugs, and no leaks. After changing the gaskets, it doesn't use an oil any more. And now that the idle is down at say 700 rpm hot, it shifts so much easier. We thought the slave cylinder was failing before as it was hard to shift sometimes, but now it is great. Also, gas mileage improved noticeably.
So, check your plugs. If they show signs of a lean mixture, do the gaskets first, you'll never regret it if you intend to keep the truck.