So I get this new to me truck last weekend. When I get it it runs perfectly. I wash it and the next day, I decide to clean out under the hood. I know enough to not use a power washer under the hood so I use an air blower and dust it then use some watered down degreaser like I always do on cars under the hood, and rinse it off with a hand operated spray bottle. After I do this the truck starts right up but misses off idle and then finally quits missing so I think I am good to go. Well, it has rained the last couple days and nights and this morning when I am on my way to work, it is missing again off idle then clears after mid range and runs fine. It is intermittent too like something still has moisture in it. Should I remove and clean out the distributor cap and the coil wire first or does one of you who has had this problem before know what it is?

 

I had a similar problem on my 1985 ram with a slant six, it could be the ballist resistor, I put it on and it ran like a top, also cleaning out the distributor cap would be a good idea, but if it's been awhile it should've dried out.

 

I don't think mine has a ballast resistor does it? It is a 91 with the electronic ignition. And a 318 btw!

 

BTW jump in it at lunch to day to test it out and Bazinga! PERFECT! I hate this intermittent crap. I KNOW it has to be something wet s it acts just like My Chevy did after I powerwashed the motor. I ended up taking off the dist cap, cleaning it out and spraying a little WD in there and never another problem....

 

Sounds like a good idea, wd 40 will help in a lot of cases, even though ur is a 318 it would've still had a ballast resistor, but since it's a 91 it might not, if it does most likely it will be right where your wire harness goes through the firewall into the cab, it would be 2 to 3 inches long and is white ceramic has 2 or sometime 4 prongs.

 

Don't waste your time looking. There is no resistor.

If there is moisture in the cap the problem will not come and go.

Check your spark plug wires. I spray them with a fine mist of water at night with the truck running.

 

Good call man, I remember finding a plug wire fault at night in my old Ramcharger and just replacing the whole set.

 

Ive seen them, I seem to remember my 440 mag in my Ramcharger had one, it was a 1974. This truck does not have one. SEAL is right.

 

Try checking the dizzy. They have been known to let water in.
And if your dizzy IS wet, make sure the hood seal above it isn't messed up enough to allow water in.

Seen it a ton in 2nd gens.

 

I like to seal my distributor cab with dielectric grease around the base and on the nipples for the wires. Never had a problem with spark in the rain/wet since I started doing that.