2009 GMC Sierra Cylinder 8 misfire

2009 GMC SIERRA
95,000 MILES • 5.3L • V8 • 4WD • AUTOMATIC
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LAX4LIFE
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  • 2 POSTS
I have had a cylinder 8 misfire on my truck for a moth and have replaced the spark plug, wire, ignition coil, fuel injector and have done intake air leak tests and compressions test and nothing has fixed it. What could the problem be, it runs rough and is making me super mad?
Sep 23, 2014 at 4:36 PM
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JACOBANDNICKOLAS
  • ✓ASE Certified Mechanic
  • 110,194 POSTS
  • ASE Certified Mechanic
Are you getting a good hot spark to that cylinder? Also, what was the compression in that cylinder and what was the max variation between all cylinders? Have you checked to make sure the injector is getting power?
Sep 23, 2014 at 7:17 PM
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LAX4LIFE
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The compression is all the same and power is going to the injector and the spark was checked and was equally as good as the others. Any other ideas?
Sep 23, 2014 at 8:51 PM
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JACOBANDNICKOLAS
  • ✓ASE Certified Mechanic
  • 110,194 POSTS
  • ASE Certified Mechanic
If the spark is good, timing is correct, compression is good, and the injector is working, the cylinder has no option but to work properly. Something is being missed.
Sep 24, 2014 at 5:24 AM
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