Hi, I have a 1997 F-150 2WD 4.2L with 218,000 miles on it. The other day, I ended up splashing through some deep water (say 6"? more or less) on the interstate (clogged drain). After getting off of the highway, it started acting like it wanted to die when I was sitting at a light with the clutch pushed in. I passed this off to the water I had gone through shortly beforehand.

However, the problem has persisted. When beyond idle, it runs great rain or shine. If it is raining, it idles fine until it is warmed up and then it starts taking periodic fits of acting like it wants to stall.

Not sure how water would have knocked something loose, but I am figuring that there must be moisture on a connection somewhere. During the first occurence, the check engine light came on. But after the weather cleared up, the light cleared itself and has not come back on since even when raining and going through the sporadic rough idling.

Any thoughts?

Thanks, Mark

 

Scan for codes to determine why the light was on. This could lead you in the right direction.
Sounds like your IAC might be failing. You can try removing it and cleaning it to see if the problem goes away. It could be totally unrelated to the water incident.
Could also have a bad plug wire.

 

Yeah, I was thinking about the plug wire. I am on my third set at this point and cannot remember when I replaced last. I replaced the IAC not long ago -- I know that does not necessarily mean the new one has not gone bad. I just thought it odd that it only does it when it is raining -- and it does not have to be raining hard.

Will the codes still show up even after the light goes out?

Thanks, Mark

 

Yes, the code should still be in there until the PCM is reset.
Sounds like the moisture could be causing a plug wire to arc.