Check codes are misfire. cylinders 5 and 7 show solid misfires. changed wires, plugs, fuel pressure reg, and injection spider. still misfires. plugs show good spark. compression good. block check good.
The Code P0300 means that a cylinder(s) is misfiring or is randomly misfiring. Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring. If no leak are found the next step is to replace the spark plugs. If the problem persist more tests needs to be done to diagnose problem, see “Possible Causes”.
– Faulty ignition coil (s)
– Clogged or faulty fuel injector (s)
– Intake air leak
– Fuel injectors harness is open or shorted
– Fuel Injectors circuit poor electrical connection
– Ignition coils harness is open or shorted
– Ignition coils circuit poor electrical connection
– Insufficient cylinders compression
– Incorrect fuel pressure
When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the Crankshaft Position (CKP) sensor signal to vary, the Engine Control Module (ECM) can determine that a misfire is occurring.