Mechanics

MODELS MISSFIRE ON #4 CYLINDER

1999 GMC Other

Engine Performance problem
1999 Other GMC Models V8 Four Wheel Drive Automatic 98000 miles

this is a 5.7 vortex engine I have replaced o2 sensors all 4, fuel injectors the upgraded ones, fuel pressure regulator, fuel filter, rotor cap and rotor, sparkplugs and wires, ignition coil and moduler, performed pressure checks in all cylinders 3x each and cylinders on 1, 2, 3, 5, 7 pressure is 180 and on 6 is 170 and on 4 pressure was 160,165,160 and replaced throttlebody gasket, intake gasket valve cover gaskets and after I tried higher graded fuel but I am still getting the same codes misfire on #4 cylinder. I replaced everything that the dealer had diagnose. What else could it be do someone out there have a clue or experiencing the same pain.
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Suburban99
June 5, 2008.



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