I am particularly stumped when I am getting reoccuring cel's being thrown with my 08 wrx. I had my intake gaskets both upper and lower replaced at the dealership that was still under warranty and had one of my injector o-rings replaced as well too among some other things that were under warranty. It was fine for a while drove it for a good stretch now the cel is coming back. before i was getting p0301 cyl 1 misfire. When the dealership did the maintenance that one went away. This time cyl 4 codes are being read from my plx kiwi that i keep in my car. I went and replaced the spark plugs with some brand new OEM iridiums. Seem to fix the problem for the next ~700 miles. Now I seem to be back at square one.
The biggest clues I can give before people start mentioning the compression test is that the CEL only triggers when it is raining outside. Also, it comes up usually when I am idling when i am at a stop light or letting it warm up. I brought it to a friends when we changed the spark plugs, and while i was out getting some new ones he tested cylinder 2 and 4 and said that they both checked out. The car has no loss in power and does not struggle to get going at all. The gas mileage has not been affected either.
Others might say that it could be a sensor? MAF, Barometric pressure sensor, etc?
Wondering if anyone else has had a similar problem or not. Subaru's sure are finicky little buggers.
Thanks for checking this thread out and I will appreciate any advice that is shared.