No Idle When Wet...

[BensBud]

I've searched for something about this a bunch of different ways and come up empty - I hope this isn't a repeat.

I have a '98 Explorer 4.0L V6 auto, bone stock (see my sig). When the weather turns wet (temperature doesn't matter) the truck will not idle at all. It starts and runs fine, but if I take my foot off the gas it just spins down to zero and stalls. It's not that it sputters and peeters out, it's just like the idle is set at zero RPM. In this condition, I have to drive two-footed. After a day or two of dry weather, the problem goes away. The first time it stalls in a corner is an eye-opener.

Just to be clear, the truck runs absolutely fine (smooth and powerful), except that it won't idle.

Any ideas of what to look for? I don't really want to take it to the dealership because they'll change the wires, the truck will have dried out and it will run fine - they'll think they've fixed it. I'm pretty sure it's not wires because it runs just fine (even in pouring rain) except for the stall.

 

[TPLYNCH]

Did you ever have the Intake Manifold O-Rings replaced under the 00M12 owner notification program? Other possible items could be the IAC and MAP sensor.

 

[BensBud]

TPLynch,

Thanks for the reply. Yep, had the 00M12 work done (at my cost). Had to tell the shop about the notification number so that they would know what to do - even though the symptoms were obvious. It was thanks to this board that I knew.

Is it worth just replacing one or both of those sensors - which would you start with? ...are there codes which might indicate which has problems?

 

[TPLYNCH]

Try cleaning the IAC first and see if there is any change. If no change, we'll go from there. I am not sure about whether the MAP sensor (if you even have one) would be involved. I can't remember what it was for. Just have a vague recollection of it causing problems like this. If I have time to search, I'll see what I can pull up on it. Anyone have any input on MAP sensor and it's function...