Misfire when its raining.......

[kaytbugsdad]

My truck has a misfire only when I'm driving and only when it's raining outside!!! I'm not seeing any moisture under the distributor cap and everything ignition wise has been replaced (cap, rotor, wires and plugs)..... Any suggestions????

 

[RF76]

I'm not sure if your truck has a barometric pressure sensor or not but the barometric pressuer does change with humidity.

 

[pwrranger88]

the coil might have a crack in it

 

[kaytbugsdad]

RF76: I'm not sure either, but I'll look into it a little further.....

pwrranger88: That sounds like good idea to look at also, since mine doesn't have the little plastic cover that goes over the coil, Maybe getting water sprayed on it from the rain???

Thanks for the suggestions, guys!!!!

 

[Mark_88]

Mine ran like a slug in the rain...definitely sounds like you're getting moisture on the wiring...if changing the coil out doesn't help, try blocking off half the rad (not a good idea for CA residents, but works OK in Canada)...the driver's side...it's usually road spray that gets mine so I've had to cover everything with rubber...and that seems to help immensely...

 

[Bryan22]

try going somewhere very dark one night and open the hood. if you see sparks you've found the problem.

Also try to keep in mind that new dosen't always mean good. I had a brand new set of wires leak spark all over the place and the truck ran like a dog. Especially if you bought cheap-o wires.

 

[kaytbugsdad]

Found the problem!!!! Coil was shorting out thru the case...... got a spray bottle full of water and sprayed the coil, it's pretty cool watching a lightning storm under your hood at night!!!! Got an MSD replacement coil, very pretty and no more misfire!!!! Thanks for all your help, guys!!!!!!

 

[Mark_88]

Mine had that too...did you replace the wires or just insulate them from the metal contacts?

Those little plastic spacers that are usually on stock engines are great for keeping the wires away from metal...and on the coil, I had to fab up a rubber boot from a Ford Tempo Distributor (they are perfect for coils) to keep the moisture away...oh, and I also relocated the coil so that it was actually under something instead of being exposed...

 

[kaytbugsdad]

I went with the MSD coil because I plan on using that along with the MSD ignition box when I do my turbo swap this summer!!!

 

[Mark_88]

I went with the MSD coil because I plan on using that along with the MSD ignition box when I do my turbo swap this summer!!!

Ah....you're going to the dark side...lol

I've been pondering that for a long time...the more I think about it, the better it sounds...but only if I think out loud...