When I have to drive in heavy rain for very long, my truck will suddenly lose power, then just as suddenly start going again. It never really dies, it just doesn't go very well. It's difficult to describe. If I stay at really low RPM, I can drive, but if I get up around 2000 RPMs (that's a guess since I don't have a tachometer), it will start doing that stalling thing. It will stall, then run, then stall, then run, over and over. Am I getting a little water in the intake or something? I don't really have any idea how to fix this, but it really sucks and I'd really like for it to not happen. Sooo... any ideas?

 

I would check the distributor cap and wires. Might be getting splash on it the faster you go.

 

Same thing would happen to me in heavy rain and right after car washes. Turns out I had a loose connector going to the ignition system from the side of the hood to the distributor. Not sure what it is called exactly, but the connection going to the unit on the far driver side of the engine bay. Being so close to the edge of the hood, water would get into the plug and block the ignition spark. Replaced the whole unit and never had the problem since. It's the only place I can see where rain water can easily interrupt the ignition system spark. Also might be worth making sure all your ground wires going to the frame and engine are tight and clean.

 

If you have a plug that isn't sealed real well against water, a little silicone dielectric grease in it before you plug it in can work wonders. Great stuff for nearly any electrical plug. Prevents corrosion on contacts, and so on. The contacts DO have to clean before you apply it, of course.

I use it in any electrical connection, including both ends of plug wires, alternator plug, starter control wire, everything. If it's an electrical connection, it gets "the grease". It's helped a lot in my two dinosaurs

Have fun, all!
Pat☺

 

Checks for leaks from around windshield doing to ECU or fuse block on left kick panel.
Splashing thorough inner wheel-well into same. There are penetrations for harness going to engine compartment, and for radio antena.

 

Oh. Interesting. This could very well be it. The driver side floor pan is completely rusted out. I cut out a lot of the rust and welded in a piece of 16 gauge, but there's still a pretty big hole where I can see the front wheel on the driver's side. I've noticed that rain splashes up in there as I drive. But would that cause it to stall, start, stall, start, stall, start...? I mean, it never dies, but it suddenly loses all power then just as suddenly starts driving again over and over.

 

Moisture where we do not want it could cause corrosion, poor contact, shorts. Not good unless you you drive this...