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Engine misfire on cylinders 2, 4, 6. 133,000 miles. steady
133,000 miles. steady misfire on 2, 4, 6. Have replaced plugs, wires, checked coil packs by switching their positions, checked fuel injectors by switching their positions, have replaced the catalytic converter. Vehicle is a 2007 GMC Yukon Denali. … read more
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I have a 2007 Yukon XL with the 5.3L Flex Fuel engine with AFM. It's 10 years old this May, and has 205,000 miles. This engine has always been an oil burner, and I've solved ignition problems before by changing fouled plugs (usually #6). This time is different. The problem started abruptly at highway speed and three hours into a 4-hour drive. The Check Engine light came on. The DIC now complains about traction control. And the scan tool shows a #4 misfire code.I've think I'm only getting an occasional spark on #4. In my troubleshooting, I discovered and replaced a fouled #4 plug that was very wet with fuel. I've replaced the plug wires, the #4 ignition coil pack, and even the right-bank wiring harness that feeds the coil packs. I also inspected/replaced all four O2 sensors (the right, pre-converter one was sooty). I've concluded that the injector and valves seem to be operating, since I'm getting smoky exhaust and the smell of incomplete fuel burn. I've put an (antique) inductive timing light on the spark plug wires, and can see that #4, while it does produce an occasional strobe it flashes a helluva lot less than the other wires.Does anybody have any suggestions on how I can further troubleshoot what I think is an ignition problem? Could the computer malfunction in such a way that it stops sending ignition pulses to only one cylinder? Could my symptoms be caused by an AFM malfunction, a faulty valve seal or spring? A rounded out cam? Another compression problem like a broken ring or cracked head? … read more
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1996 GM C1500 p/u 5.0 vortec truck parked years got to start
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oldsmobile alero 2002 v6 3.4l. when car is in drive and not moving, the car surges. feels like its not getting fuel. maybe the fuel pump or o2 sensor. could it be anything other?… read more
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1999 gmc yukon: replaced fuel pump, fuel filter, dist cap..rotor
i have replaced fuel pump, fuel filter, dist cap, rotor cap and i am still showing a code of random cylinder misfire. what else would cause this? i have a 1999 gmc yukon.… read more
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GM Tech (Cam)

GM Tech (Cam)

GMC Mechanic

5,872 satisfied customers

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Gary

Gary

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car tech

car tech

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Chris (aka- Moose)

Chris (aka- Moose)

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279 satisfied customers

16 years of experience

Paul M ASE Master

Paul M ASE Master

ASE Master Tech

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ASE Master Tech 20+ Years

Amedee

Amedee

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Anthony

Anthony

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GM Certified

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