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Discussion Starter #1
  • 2008 Silverado 5.3 V8 with AFM with 180,000 miles
  • Current issue is flashing check engine light with code p0300, snap-on scan tool reading missfires on cylinders 1, 2, 4, and 7
  • Before current issue the truck had slight lifter ticking sound and white smoke upon every start up which would go away after a few minutes, no check engine light. Took engine apart and did the following:
  • headgasket replaced
  • headgasket botls replaced
  • valve gaskets replaced
  • drivers side valve cover changed to upgraded version
  • valve stem seals replaced
  • cleaned and reseated existing valves since there was no damage
  • intake manifold gasket replaced
  • exhaust manifold gasket replaced
  • all 8 afm lifters replaced with new amf lifters
  • all 8 non afm lifters replaced with new non amf lifters
  • all lifters were placed in correct locations, previous lifters had no physical damage, rollers were in excellent shape with no gouging, only issue was a few of the amf lifters could be slightly compressed by hand
  • Visual inspected cam, turned engine to inspect each cam lob and no damage, did not remove cam
  • cam sensor replaced
  • crank sensor replaced
  • engine coolant temperature sensor replaced
  • water pump replaced
  • thermostat replaced
  • all o2 sensors replaced
  • spark plugs replaced 1,000 miles ago
  • spark plug wires replaced 1,000 miles ago
  • fuel injectors replaced 1,000 miles ago
  • did not remove fuel injectors, left attached to intake manifold during removal
  • all rocker arms where torqued to 22lbs, rotated engine for each to make sure were not installed on the head of the cam lob
- after completion of engine reassembly no longer had white smoke upon start up and no ticking sound but flashing check engine light code p0300.

- Code p0300 was for cylinder 1, 2, 4, & 7

  • moved coil packs between cylinder #1 and #5 to see if misfire would follow, no change.
  • performed a crankshaft position relearn, no change
  • performed throttle position relearn, no change
  • with valve covers removed, could see all rocker heads move while engine is running
  • performed compression test, all cylinders held at 180psi
  • Cylinder 1 misfire count of 53
  • Cylinder 2 misfire count of 27
  • Cylinder 4 misfire count of 107
  • Cylinder 7 misfire count of 58
  • with pedal pushed down n held at 1,000 rmps all misfires dissappear but return at idle
  • with vehicle on lift, ran at 50mph for 10 minutes, misfires dissappear but reappeared at idle
Any possible advice would be helpfully
 
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