1998 Chevy Truck V8 Four Wheel Drive Automatic 185000 miles
Where to start? Was starting with rough idel, but cleared up on next start, now will not run or start. I scanned code = p0300-random /multiple misfire
I checked basics, plugs, wires, fuses, ect. What all can be involved causing this?
P0300 A Random Misfire code usually indicates a vacuum leak or bad fuel
Misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.
** now will not run or start try doing below**
Get a carb cleaner and spray into the carb or the throttle body on an EFI. Did it start and die? If not disconnect a sparkplug wire or 2 and ground it to the engine -have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel problem, check the fuel pressure to rule out the fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light.
Fuel pump and Injector/s checks out-start checking the ignition system-power to coil, coil/s itself, distributor pick-up, control module, Cam and Crankshaft sensors.
If both fuel and spark is present-check the valve and ignition timing, this will lead you to problems with compression and valves opening and closing at the wrong time