What are all the things that can cause engine misfire? I have CEL codes P0300 x2, P0301, P0302. I know that means random misfire on more than one cylinder and misfire on cylinder 1 and 2. I changed all of my spark plugs last night and they were pitch black and the tip was grayish. The car still misfires at WOT and feels normal at idle even after I changed my plugs.
I just got a new VF34 and when we put on my turbo and injectors and the vacuum line that leads to my fuel pressure regulator got a hole in it that I found later after the car was tuned. I fixed the line and now the car misfires. Is it possible that the misfire could be cause by the car being too rich?
Before you ask:
2002 2.0L WRX
The car has 60K miles.
No I don't currently have a wideband its at Zeitronix for maintenance.
I'm using NGK plugs.