P0304 - Cylinder 4 Misfire Detected
P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
P0455 - Evaporative Emission Control System Leak Detected (gross leak)
Code 455 can be caused by a loose gas cap. Also look for ruptured or disconnected emissions system hoses.
Code 304 is commonly the result of old spark plugs or wires. Start with repairing the cause of that code, erase all of them, then see if code 420 comes back. If it does, suspect the driver's side catalytic converter.
SPONSORED LINKS
Thursday, April 3rd, 2014 AT 10:58 AM