found all 4 plug holes puddled with oil and when pulled, plugs where saturated. replaced all 4 plugs, oil cover gasket and pcv valve. Cleaned both battery cables and ground at transmission because of p0420 code. started the car and idled a little rough with no codes initially, then the took it on a test drive. not long after I started to drive the check eng light started flashing again. The car ran much better at high speeds up to 70 mph. When I returned with the car, in park at idle the check eng light is steady then revving the engine in park and the light begins to flash. code was the same p0304…..the p0420 code is gone. Disappointed that replacing the oil soaked plugs was not the fix..(plugs where also badly worn)…can I now swap one of the other coils with #4 to see if the code follows a different cyl?
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