Hello Scotty!
I need help with my cylinder 4 misfire (code:P0304) It started out intermittently and is now constant. I’ve changed the spark plug and checked the gap, replaced the MAF, replaced the wires, ignition coil, catalytic converter ,and both O2 sensors! It’s very severe at idle, and seems to smooth out at higher speeds, cylinder 1 rich? The computer can’t manage idle and it often will die at a stop. This is severely frustrating playing octopus with my clutch every day of the work week.
2011 Subaru Impreza 2.5I sport non turbo MT
miles:193,769mi
NGK ruthenium spark plugs gap(pre:0.044) NGK spark plug wires, ignition coil
densko Mass airflow sensor
Bosch O2 sensors
generic budget catalytic converter (auto zone)
mishimoto Aftermarket radiator
k&n air filter
Scanner used: BlueDriver
previous codes:
P0102
p0113
p0420
p0031
For the idle issue, clean the IAC valve.
For the misfire code, test the head gasket for the leaks. You may also do the compression test on cylinder 4.
Don't forget to check the Frequently Asked Questions
Bad fuel injector, clean or replace - all.
I would do a compression test before throwing money into injectors or get a noid light and go down the line and make sure they’re getting signal and you can get a long screw driver or stethoscope and go to each injector to listen for clicking indicating operation.
It doesn't take a lot of money to just clean the injectors first.
Unless you have a pressurized injection cleaner to connect directly to the rail or want to disassemble the rail and attempt to manually clean the injector that won’t work or will cost more money to have done than the above said recommendation… adding cleaner to the fuel on a vehicle with a dead skip on an individual cylinder has an extremely low likelihood of any benefit whatsoever which is why I gave the advice of looking or listening which are FREE otherwise a noid light which can be purchased for probably less than 10 dollars at any parts store.. not giving the vague advice of bad injector clean or replace all of them which if it’s not an injector concern is a great way to flush hundreds of dollars down the toilet and being a parts throwing type of “mechanic” but Thankyou for the down vote for giving legitimate cost effective advice
Any time.