Tony Tiller

Hey guys,
I have a 2007 chevy pickup that recently had a lifter fail because of the AFM. Tore it apart, replaced the lifters, valve job on both heads, put back together and got it running again.

Since back together, I have had a misfire on 5. When driving the truck, usually when accelerating, but not all the time under an acceleration, you can feel it misfire. After about 15 seconds of the misfire happening under acceleration, check engine light blinks indicating the misfire along with stablitrack, and other warnings. Assuming the computer then shuts that cylinder down because warnings don't come back up for as long as the truck is on, although it does not feel like it's misfiring then. The blinking CEL only lasts about 5 seconds and traction control warning light also turns off. If you turn the truck off and back on, same cycle will occur.

Codes I was getting was P0305 and P0171 (system too lean). Was thinking was an intake vacuum leak. Maybe didn't set right when placing everything back together or something.

Before doing that tho, swapped plugged and wires with 5 and 1. No change. Swapped coil packs and plug wires with 3 and 5 and now I get a P0300 with no lean intake code. So Now I am really confused. Excepted it to either stay on P305 or switch to P0303, but why a random misfire now and also no P0171 lean code so maybe not an intake leak?

Also, complete theory but - it seems as tho it's maybe only misfiring when AFM tries to activate based on how fast I am going. Was thinking if I just tune out the DOD, that would correct the misfire because it would never activate if that is actually the only time it is misfiring, because the truck feels normal as far as driving for a while. At idle this misfire won't show up, at least not that I can notice or that throws the blinking CEL or Stablitrack warnings.

Main confusion is why did it go to a random misfire from a miss on 5 when all I changed was two coil packs?

Any help is greatly appreciated.