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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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The first thing I would do is to double check all the electrical connectors to the ignition coils and fuel injectors to make sure they are properly seated. I know when I replaced my knock sensors, a couple of the fuel injector connectors were a royal pain in the @$$ to get them to seat properly.
 

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AFM fouls out them tr5 plugs in no time.

But why even waste the time of putting afm lifters back in? The cam is obviously worn enough to miss at idle, the rings will still float and white smoke is going to come right back, plus the afm lifters will be tapping in no time.

But screw it throw parts at it. The amount of parts replaced is astronomical when your holding a scanner that tells you the problem.
 
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Holy shit. You could have just bought another 5.3 after all that.


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