Originally Posted By: macdole99
hey guys i have an 02 tahoe 5.3 flex. when driving above 50 or over 2500 rpm, the check engine light flashes and i get p0300(random misfire). i have changed the plugs, fuel filter, both upstream 02 sensors, cleaned the maf sensor and cleaned the fuel system. i sprayed the intake manifold with maf cleaner to check for leaks but didnt notice a change. and other ideas? thanks guys!!
If this code comes up more than once after a reset then it should eventually settle down to one specific cylinder. Swap coils around to eliminate them, the wires are suspect if not GM OEM, then the triggers (cam and crank) are next. Then check valve springs and such.
This can be a bit vexing, but it is very serious. It can be some really bad and expensive things, like a bad lifter eating the cam, etc.