ok so i bought the car from an auction check engine light was not on (i assume since the car had to be jumped to get through the line) she is an 02 sable ls premium with 65k miles. check engine light started flashing i assumed the normal misfire and had her plugs wires and even the cylinder #4 fuel injector changed. still she was throwing p0304 and p0305 at me.
didnt even get to leave the mechanic and the CEL
was on steady now and also flashing for the random misfire. i left her there. he did a compression test and it showed that cylinder number 4 was at about 100. so clearly there is a compression issue and there is a leak somewhere.my mechanic assumed my exhaust valves were dirty and just not seating correctly at low idle due to the condition of the motor and amount of miles he and i hope and highly doubt the valve is bent/burnt or has a broken ring. he removed the exhaust manifold (headers as some would say) and sprayed the valves with some seafoam and tried to clean em up. he said they were pretty caked up. (at least this is what he told me)
i tried running some seafoam through the throttle body (although half of it didnt make it in because i messed up) and that didnt work so i shall try this again
i put some marvel mystery oil in the motor and in the gas tank (i have only used about a 1/4 tank so far) light is still on
i even tried an old school mechanic trick someone told me and put some water in the throttle body in hopes of the steam cleaning the motor. light is still on.
im no mechanic but i would like to believe it is due to buildup on the valves seeing as the car runs flawless on the highway.
however when i get off the highway and sit at a red light she misfires and starts flashing. does not flash while on the highway only at low idle.
p0304 and p0305 are the only codes coming up period. there are no other codes stored or pending. i was told by another mechanic there are no vacume leaks as the car would be throwing lean codes at me
if i had a bent/burnt valve or bad ring wouldnt the car still misfire at higher speeds while on the highway?
please someone help before i throw any more money into this car.