the check eng light came on and i was told i had to reset the eng.flash the firing order or somthing like that. i replaced the wires and plugs but still cant get it to run right. the codes say i am mis firing in # 4 cy but the volt meter says its fine. how can i fix the problem.
hi i have a 2002 gmc yukon 4x4 3/4 ton with a 6.0.
- Thread starter blairstop
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about20ninj45
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Have you checked your plug and wire going to that cylinder?
zraffz
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Unbolt the #4 coil and replace it with the #6 coil... Does the scanner now say #6 misfires? If so, it's a bad coil pack.
This^^^^^
rockola1971
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I just wanna know how "the volt meter says its fine"? Have a DC voltmeter capable of measuring 20kv plus do ya?
retiredsparky
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A multimeter is only marginally helpful diagnosing high voltage ignition problems. The swapping of the coils is the easiest way to determine if the coil is bad. If the problem moves to the new location when you move the coil, then the coil is the problem.
rockola1971
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I hope you mean resistance. The 9v battery in your multimeter will not find a partial short to ground, it will "see" a dead short.
If one cylinder only is missing there are really only 3 possibilities, bad spark, bad fuel injector or bad compression.
My diagnostic routine goes like this;
1) Connect my old dinosaur inductive pickup timing light to the spark plug wire on the missing cylinder and fire up the engine, if the light blinks while the engine is running I know that I have spark; if not I switch around the coil packs and see if the miss moves to another cylinder.
2) If it passes the spark test I pull the plug and look for oil or a way out of spec gap, if the plug looks operable I remove the plugs that are adjacent to the missing cylinder, connect a compression gauge to the missing cylinder and spin the engine over; if compression seems adequate then I conclude that the only thing left is a bad fuel fuel injector so I replace the fuel injector on the missing cylinder.
Takes about 15 minutes to do this routine plus whatever time it takes to replace the failed component.
My diagnostic routine goes like this;
1) Connect my old dinosaur inductive pickup timing light to the spark plug wire on the missing cylinder and fire up the engine, if the light blinks while the engine is running I know that I have spark; if not I switch around the coil packs and see if the miss moves to another cylinder.
2) If it passes the spark test I pull the plug and look for oil or a way out of spec gap, if the plug looks operable I remove the plugs that are adjacent to the missing cylinder, connect a compression gauge to the missing cylinder and spin the engine over; if compression seems adequate then I conclude that the only thing left is a bad fuel fuel injector so I replace the fuel injector on the missing cylinder.
Takes about 15 minutes to do this routine plus whatever time it takes to replace the failed component.
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