RomanR
New member
hi, my name is Roman, I have a 2007 GMC Sierra 1500 5.3L crew cab. a few weeks ago I received a misfire code P0304, P0430, and P0121 code. the engine started knocking so right away I changed out spark plug wires coils, TPS sensor, and spark plugs. The spark plug in the # 4 cylinder was partly black. I gaped the new plugs at .050, checked the compression on the engine (compression was good at 185-190) I also cleaned the air intake then checked my codes and now reading P0300, P0507, and P0171. I was not sure what else to do and after talking to friends that are mechanics they said that it may be an air sensor. I took it to a shop and they are telling me that one of the lifters is shot and I need a new engine. but other mechanics are telling me to get a second opinion. I am not sure what to do can anyone please help me out. I am a backyard mechanic and would like to find out more info on this issue.
Thank you
Thank you