So i have been getting misfires between 2~2.5 RPMS. Check Engine Light came on checked the code P300 (Random Misfires). I have replaced my plugs. I checked my ignition coils and they seem okay. I pulled my MAF out and cleaned it. While my MAF was out it seemed to be running the same so i thought maybe it was the MAF so i went and bought one just in case. I put the old one back in and i checked the CEL and i pulled a MAF code. I bought some Seafoam and used it on the car and seemed okay at first but as i try to WOT it misfires pretty bad. Got home checked the CEL and i pulled the coded and im back to P300. Any suggestions?? Oh and i just put the Seafoam in. Do i run it a little more to see if itll get better or is it an immediate fix??

 

Lnf? How many miles? Ever have the valves cleaned?

My guess is valve gunk

 

yeah it is LNF. its got 195k miles?? dont remember exactly but something like that and no i dont think its ever had the valves cleaned. i havent anyway im not sure about the previous owner

 

Wow an lnf with 195k miles, trying doing a compression test what are your plugs gapped to?

 

Seafoam isn't going to do anything to the intake valves on a Direct injected car lol.

 

Leak down test and clean your coked intake valves and valve runners

 

i have not tried doing a compression test but i think im gonna have to now that you mention it. Better safe than sorry and im gapped at ~35

 

sorry about that i got my cobalts mixed up. ive got an LSJ not an LNF

 

Yeah just do a compression and leak down test the gap seems to be correct not very familiar with the lsj tho

 

So i did a compression test and the leak down. Compression test Cylinder 3 & 4 were about 180-185ish while 1&2 seemed to be ~200. So when i did a compression test cylinder 3 was okay but cylinder 4 wasnt. The air seems to be coming from the fuel injector area or the spark plug hole not too sure. Any suggestions??

 

anyone??

 

Are you saying you can feel/hear air coming out somewhere when you do the compression test?