I have a 1997 subaru legacy and the "check engine light" came on. The car started shaking back and forth so I got the code read and it was a cylinder one misfire. The problem I am having though is that the car seems to be firing on all four cylinders when it is warm/hot outside, but if it is raining or damp I get the same shaking problem.

 

Anyone know why moisture might be causing my first cylinder to misfire?

Hi jonw15 and welcome! Based on your description of it happening primarily when it's damp, I would definitely check the spark plug wire. Check for any cracks or fraying. The plug wires are easy to find as the coil pack is right on top of the block. If you're not sure which is the #1 cylinder, just look at the top of the coil pack - the cylinders are numbered.

 

Also check the connectors going to/from the coil pack, maybe jiggling and reseating. Sometimes if the spark plug wire or coil is bad, if you get the engine running in a slightly dark place and get the problem to occur, you can see some arcing from the wire/coil pack to ground.

I've checked the wires and there seems too be no fraying however on the coil pack I've noticed that 2,3,4 have a nice brassy tip to them but the cylinder one part of the coil pack is kind of brown definetely not shiny like the other three. Could that be my problem?

Hmmm interesting....well I would maybe try cleaning up the #1 connection with scotchbrite or something, check the spark plug wire's connector to the coil too and make sure that's good and clean and tight, and put some of that dielectric silicone grease in there and plug it back on and see what happens? You can always simulate by (carefully) spraying some water from a squirt bottle or something onto the suspect connections to see what happens.

I had the same problem it was the spark plug wires. Even though there was no apperent damage to them.

I sprayed a bit of water on the coil pack around the cylinder one part and I got some sparks flying off around there. Is that the signs of a bad wire, bad coil pack or both?

 

btw, thanks for all the help you've been giving so far

Can you see where the sparks are coming from? If they're originating on the plug wire, I'd replace those; if they're originating from the coil pack, then you may need to replace it. Sometimes the coil packs get carbon traces on them. A temporary fix could be to wrap electrical tape all around the area where you saw the sparks coming from; I did that for my brother once 'til he could get it fixed. On these Subaru's this sparking issue I think can impact the opposite cylinder as well as I think it sparks cylinders two at a time.

This is a typical of a vlotage leak at the coil or bad wires. Replace the wires first since they probabaly need replacing anyway. DO the water test again and if you still see sparks replace the coil.

 

 

nipper