Engine Performance problem
2001 Pontiac Sunfire 4 cyl Front Wheel Drive Automatic 227106 miles
i have come up with code P0300 misfire detetcted by pcm. I have changed, camshaftsensor, crankshaft sensor, coils are firing, pump sounds likes running, smell gas, I have completed a compression tets on the engine 1 cly -60psi, 2cly-40psi, 3cly-60psi, 4th clyis 120psi. I'm not sure? Is it the timing chain, but heard they are dont uselly dont break that quickly, in the past it heated acouple of times, changed coolant sensor, fan relay, thermosatate. It seem to work for a bit overheated agin and wont start.