I got a 2008 Colorado inline 5 3.7L that has a P0300 code. I came to find out that the 04-07 had issues for cylinder head not sealing valves correctly requiring a new cylinder head replacement. That scared me as I do not have the money for this at the moment. When I got the vehicle it had P0300 and P0303, I replace spark plugs and P0303 disappeared. Cylinder 1 had oil all over. I replaced the valve cover gasket to come and find out there was no issue with the tube seals. That scared me even more and had me worried it was going to be the cylinder head needing replacement. I did a compression test and my results were cylinder 1 - 165 PSI, 2 - 165 PSI, 3 - 180, 4 - 185, 5 - 185. This is within a 10-15% PSI difference from each other. Okay - Good compression. This clears engine internals are fine. Spark plugs are good, compression is good. I removed spark plugs and noticed there was oil on threads, I put 2 and 2 together and just figured the thread on cylinder 1 were dirty and got the plug oily/dirty again. My next plan of attack is coils and injectors? During compression test I got P0301 and the P0300 disappeared didn't come back [maybe for time being] (i cleared codes before doing compression test). I swapped coil 1 and 5 [broke coil stud so currently waiting for my drill battery to charge so I can extract boot stud]. Any ideas on what could be going on?
u/AbiesPuzzleheaded831
I got a 2008 Colorado inline 5 3.7L that has a P0300 code. I came to find out that the 04-07 had issues for cylinder head not sealing valves correctly requiring a new cylinder head replacement. That scared me as I do not have the money for this at the moment. When I got the vehicle it had P0300 and P0303, I replace spark plugs and P0303 disappeared. Cylinder 1 had oil all over. I replaced the valve cover gasket to come and find out there was no issue with the tube seals. That scared me even more and had me worried it was going to be the cylinder head needing replacement. I did a compression test and my results were cylinder 1 - 165 PSI, 2 - 165 PSI, 3 - 180, 4 - 185, 5 - 185. This is within a 10-15% PSI difference from each other. Okay - Good compression. This clears engine internals are fine. Spark plugs are good, compression is good. I removed spark plugs and noticed there was oil on threads, I put 2 and 2 together and just figured the thread on cylinder 1 were dirty and got the plug oily/dirty again. My next plan of attack is coils and injectors? During compression test I got P0301 and the P0300 disappeared didn't come back [maybe for time being] (i cleared codes before doing compression test). I swapped coil 1 and 5 [broke coil stud so currently waiting for my drill battery to charge so I can extract boot stud]. Any ideas on what could be going on?