Q: Why do i keep getting the po300 code after replacin plugs,wire,coil packs and cleaning throttle body. i have checked fuel pressure

P0300 signifies that there are random misfires. Consequently, there is usually a "global" cause and there are quite a few such causes including: fuel injectors that are defective, EGR valves or tubes that are clogged, ignition timing that is off, vacuum leaks, head gasket(s) that are leaking, camshaft sensor that is faulty, crankshaft sensor that is faulty, mass air flow sensor that is faulty, oxygen sensor that is faulty, throttle position sensor that is faulty, catalytic converter that is faulty, and PCM is faulty (very rare). A real time scanner can eliminate some of these possibilities and the others are fairly easily tested. If you want the necessary diagnostic steps performed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a misfiring diagnostic and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.