would a damaged valve or valve seat cause a P0300 engine code

Question

Also showing codes P0121 and P0123

Answer 1

Hi there

Damage valve seats or a valve can cause a misfire. Usually though it would be a single cylinder misfire for that particular cylinder. This code indicates either multiple misfires or that the computer cannot determine which cylinder is misfiring. The other 2 codes indicate there is a problem with the throttle position sensor. You might want to check the ground wires from the back of the engine to the firewall. Sometimes they break on these and can cause the throttle body codes.