Misfire problems when weather is wet.

[94RedGt]

Hey guys my car has been giving me some trouble since the last few days that it has started raining out and its humid outside, when i leave the car out in the wet weather raining or not after a few hours when it has cooled completely i get in it and start it and the whole car shakes a lot and it gets worst if i give it gas, apparently its a misfire , after driving until it warms up the shaking goes away and i feel that my engine has more power .

What should i start checking for ? To me it seems that the humidity is getting into the distributor or something with the ignition and that until it warms up it wont run right. Both O2 have been replaced with NGK ones, all 8 sparkplugs are brand new Autolite 25's , only thing that i havent replaced in the ignition are the Coil pack, cap and rotor , and the wires, i did not replace them cuz they are MSD brand and i figured that they are still not bad but after this im just going to replace the plugs and cap/rotor anyways just to be sure. Car has always run good in the rain but it looks like it does not like humidity since before it was already hot when i drove it in the rain.

 

[framda]

Start with the cap and rotor, try the plug wires if that doesn't fix it. You can try to get somebody (that you trust) to powerbrake it at night. Sometimes you can see the plug wires arcing to ground, that will tell you right away if it happens. Did you check for hard or soft codes while it was doing it? You can also try the cylinder balance test that the EEEC IV system will do with the onboard computer. Check out the sticky on pulling codes without a scanner, or use a scanner if you have one. Another trick that we did on race cars is to check the temperature of the exhaust header right were the hot gas comes out of the head. Use a digital pyrometer. Not every one has one but if you have a friend in the heating and air business maybe they could lend you one, they use them to. When you find the cylinder that is colder, that is the one missing. Good luck.

 

[94RedGt]

Found the problem or atleast i think i did, so basically i got to work today and decided to open the hood and see what could be causing the problem, well just as i put the prop on the hood i noticed two of my drivers side sparkplug cables resting in the headers, one is basically fudge and the other one was not melted, stupid me decided to try and move the cable with the engine running and got a really nice shock of current from the melted cable, scared the crap out of me and the shock hurt a bit, going to buy new cables and rotor with a cap and see if the car still misfires, but that had to be it, opened sparkplug cable is sure to cause trouble.

 

[CC'S95GT]

I LOL'd about grabbing the spark plug wire.I hope that fixes it for ya.Let us know either way.

 

[framda]

I used to have a neighbor that had three sons. He ran a small engine shop out of the back of his house. Whenever he needed to check for spark he would call for the son that had been the last one to piss him off. Punishment was holding the wire and it was obvious if there was indeed spark. I saw them piss there pants a couple of times.

 

[94RedGt]

What wireset should i get ? Should i get one of those performance ones or a cheaper factory replacement ? The ones i had were msd but in my honest opinion i dont think sparkplug wires do anything besides look good under the hood.

 

[framda]

I like OEM unless you have circumstances that dictate a need for something special.

 

[94RedGt]

Ok all done, went to local autoparts and got a new MSD cap and rotor kit and some Accel universal wires, trimmed them to size and used some separators to keep every cable off the exhaust and to make it look a bit cleaner, and wow car has gained a bit of topend now, pulls stronger than before when rpms go above 4000, runs alot smoother now too, next mods are going to be removing the smog pump(florida FTW) and fixing an annoying valve cover oil leak and another oil leak that appears to be coming from were the oil pressure sender is located.