06 Hammer H3, 87,000 miles, inline 5 engine. Got the P0300, multiple misifres. I've changed the sparkplug, coil pack, VVT solenoid, cleaned the throttle body and MAF. I don't know what else to do. Any ideas?
Those things are notorious for having fuel injection problems. GM made them with cheap plastic and the fuel injection parts, so when they get to be older, after 10 years old, the plastic cracks, leaks, and gets multiple misfires. That’s a typical problem with that.
It can be hard to diagnose the P0300 code yourself. It can easily be the injection system and that is a very complex system. You don’t want to take the whole engine apart yourself, which you’d have to do to get to the injection system. My recommendation would be to have a professional technician, diagnose Check Engine Light for you and make the necessary repairs.