Thread: Why does my car run like $hit when damp/humid or raining outside?

Surge & hesitation, fluctuating idle, shuddering most anytime it's either extremely humid or raining outside. It's a '98 SE-R w/ most bolt-ons, original DE motor. It just feels off.

I guess what I should really ask is, has anyone else had any similar issues, and if so, how did you rectify it? MIL is on but it's always been on. The car runs fine on dry days.

My first thought is plug wires...the added moisture when humid would be the perfect conductor. Easy to check at night when dark...use a squirt bottle and MIST a spray over the wires and look/listen for sparks/arcing.

Good call. I just changed the spark plugs when I slapped some cams in, I will grab some new wires soon. Thanks for the input!

It is probably your distributor cap seal. They tend to break over the years and it allows moisture inside the dizzy. This can mess up the readings of the cam angle sensor and make the car feel sluggish, or just get the cap and rotor wet and make less spark.

I've had this problem with multiple dizzy's throughout the years.

Also the distributor cap is another common one for damp poor running issues. They crack over the years from the heat, and the cracks let moisture in.

Could a bad ground cause this? Maybe a ground point is rusted? Weren't you having an issue with a remote breaker or something like that?

I don't think so, because since water is a conductor, if there were an intermittent ground, water would help complete the circuit. Unless there was an exposed wire and water was then shorting it to ground. But I think that's less likely than what we've already mentioned.

If you are running too far to the rich side, it will be exacerbated by humid weather. Humid air is thin...less o2 than dry air.

Actually, the last time I changed my plugs it was clear that the car runs on the LEAN side. So now I'm even more confused

I wish I ran on the lean side. I have no idea what my car runs...