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1998 GMC Jimmy Misfire cylinder 1

Tiny
TRASH7070
  • MEMBER
  • 1998 GMC JIMMY
  • 4.3L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 102,000 MILES
My truck runs rough and emission engine code P0301 indicates a misfire in cylinder 1. ERG valve is cleaned and PVC valve is good. Mass Air sensor was replaced about 5,000 miles ago. Oxygen sensors were replaced recently. The fuel pump sending module, fuel filter, tank, filler neck and fuel lines all were replaced. The distributor cap, rotor, spark plug wires, plugs appear to be good with 25,000 miles on them. Stepping on the accelerator does not smooth out engine, has a lack of power. Fuel pressure regulator is new. Plenum gasket and throttle body gaskets are new. Throttle body and idle solenoid are is clean. Cylinder Compression was 170 psi on cylinder 1 and 5 and psi on cylinder 4 and 6. Didn't remove plugs on 2 and 3 because they were difficult to get at.
What do you think the problem is?
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Friday, January 2nd, 2015 AT 7:17 AM

2 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Misfires are very hard to diagnose and shold be left up to a pro check fuel pressure with a gauge shold be 60-66 psi also see if rotor on dist with move it shouldn't if it does pull dist an dlook for worn dist teeth
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Friday, January 2nd, 2015 AT 9:39 AM
Tiny
TRASH7070
  • MEMBER
  • 2 POSTS
I repalced the fuel injectors (spider valve) and the misfire was gone. I think the #1 poppet valve (injector) was clogged and not spray gas into the cylinder so it was running lean.
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Friday, January 2nd, 2015 AT 5:08 PM

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