Multiple misfire

Tiny
FREDDIFRED
  • MEMBER
  • 2002 GMC SIERRA
  • 6.0L
  • V8
  • TURBO
  • 4WD
  • AUTOMATIC
  • 80,000 MILES
Okay, so I did a head job I actually put LS1 heads on my lq4 with all new plugs, wires, fuel injectors, ls1 intake manifold, msd d585 coil packs with a single turbo kit. It has a t4 turbonetics hurricane sylvania. Brand new exhaust manifolds crossover 40 mm turbonetics evolution wastegate 3 inch pre axle exhaust. I also did the o2 sensors. I did the electric fans upgrade and put a 185 amp alternator got it all together today and I have misfire in 3 and 6 piston. Idles badly and takes off choppy but once the turbo spools up it’s a rocket opens right up? Once it comes back down though it’s misfire only in 3 and 6 a lot? Also high idle and stinks like gas? It has no catalytic converters and like I said I did all the o2 sensors even though I turned off the back ones and deleted the EGR and EVAP sensor from the intake as well is off the ECU. Any ideas? Maybe fuel pump? Or could it be a new faulty injector or injectors or faulty o2? I’m kicking myself over here any help would be great. Thanks in advance!
Wednesday, April 14th, 2021 AT 11:15 PM

1 Reply

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning,

The first thing I would do is to check the compression in the cylinders. Make sure you have 140-160.

https://www.2carpros.com/articles/how-to-test-engine-compression

I would also check the fuel pressure as well. I attached the spec for the pressure below for you. It may be running lean at idle.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Roy
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Thursday, April 15th, 2021 AT 2:08 AM

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