I had a p0300 for cylinders 1,2,3 and 4 changed plugs, wires and checked coils were ok but still getting misfire in 3 and 4 no other codes




Fisi, August 4, 2020

You may have the following issues: 

Faulty spark plug
Faulty ignition coil
Clogged or faulty fuel injector
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

Check all of these, and let us know if any of these options have solved your problem.

First swap the ignition coil and spark plug.

Don't put them in one cylinder, for you put the ignition coil #3 to cylinder #1,

and place the spark plug #3 cylinder #2. this procedure lets us determine whether the ignition or the spark plug is faulty.

If the misfiring move to any  of the cylinder where we place the ignition coil or spark plug, It means the ignition coil or spark plug.

And when the the misfiring stay on the same cylinder need to check further more