Jland78

This is a 90 with new plugs, wires and cap that were all installed about 6 months ago. Car was running fine until a heavy rain came through and now it is misfiring. Unless the heavy rain is just coincidence could moisture have gotten into something. The cap is on pretty snug. Any ideas?

s carter

If you feel Confidant that the Ignition is Good, Draw off a Fuel sample either using the Test port or Siphoning from bottom of tank. Look for a layer of water in the gas, Some times the weeper tube in the Filler neck gets overwhelmed and I have seen water get in.

ex-x-fire

Get it in a dark place, wet down the wires & cap, look for spark jumping to ground.

MatthewMiller

I just went through this on my 96. I was convinced it was the optispark or module. It turned out to be one of the two pre-cat O2 sensors. It really presented like an ignition problem, though. Granted I have long-tube headers that put the sensors close to the water on the road. But O2 sensors are cheap these days if you want to throw parts at it, especially if they are old. If you can data-log your car, run it until it is in closed loop and see what the a/f numbers look like on each bank. If one side isn't responding at all or looks laggy, that's probably the issue. You should probably be getting a diagnostic code for this, though. It's a long story, but I didn't immediately get a code, but if you have the stock ECM in your car you should be getting something. I think on mine, water got into sensor through the stopper where the wires go into the top of the unit.

scrappy76

were you driving it at the time of the heavy rain ?

James84vette

Yeap, check your plug wires.

aklim

Make that a dark place and a fine water mist AROUND the wires.

Jland78

Thanks for the replys. Been working a lot. Ill post back what I find.