P0304 Toyota - Cylinder 4 misfire persists

Question

Have replaced the main air intake/hose, top of the line plugs and wires, new coil pack, cannot find vaccume leaks in any hoses, have put in fuel injector cleaner on current tank of gas, there are no O2 codes thrown so was advised that the O2 sensor probably isnt the problem.. Only code being thrown is cylinder 4 misfire. The problem is inconsistent; it will smooth out but mostly runs rough due to misfire.

Any experience with this and/or suggestions are greatly appreciated.

Answer 1

P0304 Misfire number 4 cylinder

Check fuel injector connection, this is one of the most commonly overlooked area. If you can rule out a mechanical condition by doing a leakdown of that cylinder it would be better., You can also swap out the fuel injector and see if the misfire follow , if it does replace the fuel injector

 Here a fuel injector connection that came out do to its locking tabs being non operational. just doing a visual you can see the fuel injector was not making proper connection this cause a intermittent misfire condition