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Intermittent idle problem - 1999 Ford Explorer

My 1999 Ford Explorer XLT, 133,000 miles, has acquired an annoying problem recently. It is annoying because it is intermittent and unpredictable. Some afternoons when I start it, it will immediately die if I don’t maintain idle speed by pressing the accelerator lightly. Even at highway speed, the engine will die if I take my foot off the gas, leading to some exciting commutes home. This happens only occasionally and I haven’t been able to correlate it with any particular weather condition. It often resolves itself after about 30 minutes of driving. One mechanic cleaned the throttle plate to see if that made any difference. I have dumped a couple bottles of gas treatment in the tank too. The Ford dealer says it’s a shot in the dark but he could try replacing the idle air control valve for $250, but his advice was to wait until the check engine light came on. I can continue to drive it like this, but it’s not entirely safe and I would never entrust it to my teenage daughter. Any ideas?

Your IAC or Idle air bypass valve as Ford calls it is sticking. You can clean it and it probably won’t stick again for six months or more. Or, you can replace it. It is an $80 part and very easy to replace. Go somewhere other than a dealer if you don’t want to do it yourself. Next time you have the stalling problem, tap the valve a few times with a hammer and it will probably unstick for a while.

thanks very much for the advice! I’ll try the hammer first - can you tell me roughly what I’m looking for under the hood?

First you have to tell us what engine this has, 4.6l V8? If your IAC has never been replaced, that is a prime candidate for this problem. I am having some trouble matching it to the symptoms. Typically when they are in their early failure mode they are more troublesome when cold and improve when warmed up so the biggest problem should be in the morning rather than in the afternoon. In addition. The engine should not die at speed, only as you come to a stop.

At any rate, replacing the IAC should cost you $100 or less if you do it yourself. I would use a screwdriver handle to tap it rather than a hammer, unless you have a very small hammer.

This might be what your IAC looks like: