Engine misfire under load, especially when cold?
Car is an 06 Chrysler 300 3.5 with 113 000km. I have been experiencing a miss under load for quite some time now. Cylinder 5 miss with code p0305 only. Miss occurs most often when the engine is cold going up steep or long hills, and usually happens right after an upshift. Does happen when warm but not as bad. If I hold the car in 3rd and don't shift, it doesnt miss, but surges slightly. Miss is very intermittant but becoming more frequent.
Here is what I have done already:
Changed/swapped coils
Changed spark plugs twice
Decarbonized engine and valves
Replaced plenum gasket
Removed fuel injector to check spray, but did not clean externally
Ran injector cleaner in several tanks of gas
Cleaned egr valve ports
Checked for vacuum leaks
I am thinking it may be the injector, as this is the only thing that has not been ruled out by swapping or replacing. Have not checked compression becaus mechanic said it would cause a constant miss. Anything else I should check besides injector?
I checked the codes myself. There are no plug wires, as this is a coil on plug system.
Thank you robert M, but I already cleaned the throttle body (forgot to mention that) by removing it and scrubbing it with cleaner. Also my car does not have an idle air control valve.