I have a buddy who's car is almost having my similar problem, except when its going to rain or already has rained, his car wont start but will try too, it gets fired up to where the starter grinds if you try again, but its only spitting and sputtering very badly to where its not even sounding like its running, just choking before it dies a couple seconds later. The throttle body when you open the blades to look in burps out steam or vapors it looks like. And the coil shows spark when he held a screw driver to it (not exactly the best way to test it) so we're kinda lost. Car is a 95 Z28.

EDIT: btw, there are no DTC's like 16 or anything like that. None at all.

 

This just in,,,, He forgot to tell me that when it does run on a normal weather day, the motor seems to have a certain "surge" to it every few seconds or so and there is an intermittent ticking noise from the passenger side valve cover. He also has the fuel smell coming from the dipstick along with hard cold starts, almost everything my car is doing except for the spitting and sputtering in the rain. Mine just simply doesn't fire at all. Say's that rarely but sometimes, there is a very slight hesitation. And on occasion there is smoke out of the tailpipes, usually greyish color and reeks of gas.

 

Well some mustang boy's have told us they think it could be a broken valve spring causeing a valve to stick open when the oil is cold, pretty bad gotta rely on the stang guys to get a response . Oh well, thanks anyway. That makes sense, but still doesn't explain why its not starting in the rain.

 

You need to clear up the crankcase contamination problem before you wipe out a cylinder. He or you probably has a dead cylinder and when it's humid, loose one or two more. Since your oil is contaminated, look for spark problems.

 

will do slopo. Would a spark problem still be possible if the car runs fine when its actually running on a non rainy day?? I do have a slight finger pointing towards the ignition system myself. Just wondered if there would be any way that there could be spark problem on non humid day's that would be present when it is humid.