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The vehicle has a very slightly misfiring at idle and when you snap the throttle you can feel the misfire intensely.
The vehicle has new spark plugs and wires but the spark plug from cylinder 4, although it had recently been replaced, was black (like burnt).
The costumer said that the spark plug from cylinder 4 has this problem for a long time now.
In other words, even if I put new spark plug on cylinder 4 it will get black (like burnt) in a week.
Can an O2 Sensor Slow Response cause misfire?
Should I just put a new 02?
Fuel injector, compression or O2 slow response issues can cause the new spark plug on cylinder 4 to get black (like burnt) even in 1 week?
Last edit: 6 years 3 months ago by Bobby10. Reason: Now Check Engine Light is ON
I think I would start with a compression test or leak down test, misfires at idle that are less noticeable at higher RPM always make me look to valve issues.
Also with Honda engines valve seat recession can be an issue causing the valve clearances to close up.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
bobby10 wrote: Fuel injector, compression or O2 slow response issues can cause the new spark plug on cylinder 4 to get black (like burnt) even in 1 week?
The plug is likely getting black from incomplete combustion. A sticking open, or leaking injector could cause this. Also, low compression, weak spark and probably a hundred other things can also.
It isn't likely that the O2 sensor would, as that would affect more than the single cylinder.
Did you check the compression? Check all 4 cylinders, so we have something to compare to. Check with fuel disabled, cranking the same number of revolutions (at least 6-8 complete revolutions) and with the throttle wide open. Let us know.
and welcome 
