Electrical gremlin!
 

Here is the history:

Took car to car wash last week. I never go to these, but it was the touchless style. The car was running, and when the machine sprayed in the front of the car, it stalled. I have a Roush bumper, and it is a lot more prone to water getting in. BTW, my low coolant light came on too. It ALWAYS does this after washing under the hood, but I did not do this on this ocassion. I have always suspected a wierd electrical problem associated with water and the coolant light.

I had a hell of a time getting it to start and when it did, it ran like crap. I suspected wet coils. After opening the hood, water did not appear to get into the plug areas at all, just down in the lower area.

After letting it dry for 3 hours with the hood open, I could drive the car, but the idle was horrible. It would want to idle at 3,000 rpms. If I unplugged the TPS, it would make no difference at all. So, I figured the TPS got shot and it was a coincidence.

I replaced the TPS and car ran fine all week.

Saturday night, I wash the car in the driveway with the hose. I don't recall if I ran it after that. Wife takes the car this morning and comes in the house saying that the coolant light was on. I told her not to worry about it and told her just to drive it.

On the way home, car starts to idle again at 3,000 rpms.

After she gets home, it sits for a while. I take it out three different times and it ran perfectly.

What the heck is going on here? There seems to be a connection between water, the coolant light, and bad idle. Does anyone have any ideas?
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Re: Electrical gremlin!
 

I would say you have a short to ground somewhere.

Either through the water itself or possibly a rise in heat due to humidity. (heat expansion)

Electrical gremlins have always been a beast.

The only thing I can recommend is to see if you have any codes coming up in your ECU... Other than that, its gonna be old style troubleshooting with a circuit tester and multimeter.

Re: Electrical gremlin!
 

Another thing to check for is...rubber grommets that have worn away on the firewall/engine compartment exposing metal which may also wear away insulation on the portions of the wiring harness. just another thing to check for if you haven't fixed the "gremlin" yet...

Rubber grommets are often overlooked unless you've had a "gremlin" before...I went through hours on my old 1985 GT before I found the problem.