I have a question about my 97 Z28. When it rains or I wash my car the check engine light comes, but then goes off after a while. Any ideas on what would cause this?
Thanks!

 

well could be a few things, if you have a cold air intake, it could be sucking the water in when it rains, temporaily throwing check engine light, or it could be the opti not liking the water too much....could be other things though

 

no its all stock, and just changed the opti and that didnt help

 

should have some info stored in the computer. have it scanned for trouble codes. should give u/us a better idea were to look.

 

does any region in the engine area look to get really wet, water in plug sensors etc would cause the light to come on if there are misreadings, just because you mention it doe sit after a wash?

Does it only do it on start up in the rain and after a wash or does it come on after driving say 20 mins??

 

Well I haven't really checked for water, it starts running really rough instantly, then a few seconds later the check engine light will come on

 

i was getting water in my ecu and it was doing weird stuff like that. it did finally quit and wouldnt run. so have u had it scanned for trouble codes yet?

 

well it sound like what craby says of something, water is getting into electronics when stationary and mesing stuff up if it does it when started

 

Yeah it comes up with a random cylinder misfire

 

this points to the opti, wires, or plugs are getting wet or moisture in them causing a bad spark and hence the missfire, unless as craby says its in the PCM and its causing the car to go 'mad'