My first visit to this thread and I did read all the posts.
First and foremost, thank you for your service.
I want to say that the purpose of my post is for
positive constructive criticism. In no way shape or form am I trying to take you away from your progress, you will surely know more about these engines than alot of us here after you get her running again. This is a great thread, and you are surely dedicated in getting this motor back up and running and you will be
WAY ahead of the game with everything cleaned up, tightened up, many new parts here and there so regardless of the root cause, you will have a near-fresh motor.
What concerns me was the multiple mis-fire and your #2&5 cylinders having some more soot than others. I know that this is a moot point for the most part given my impeccable timing to visit this thread....
I'm no expert either just throwing some of my $.02 around.
Mooseman said:
It could be possible that a misfire could be caused by an intake leak. Could also cause extra carbon buildup when the engine might have been trying to compensate by throwing more fuel into the affected cylinders. Also possible that the near overheat didn't cause a blown gasket at that time but just started it on its way to eventual failure. Pieces of the mystery sure seem to fit.
Good point....I thought this as well but there would be compensation for all the cylinders if I'm not mistaken.
I honestly think that a can of BG44K would have possibly worked wonders here. This stuff cleans carbon like crazy. You may have a sticking injector, possibly an air leak but this looks like a normal head with normal carbon build-up.
What kind of fuel are you using? I'm going to guess a steady diet of 93 octane.
The low compression is another concern, could very well be a sticking valve, the areas of higher carbon around these cylinders could hold one open slightly as someone else pointed out.
When you replaced the plugs, did you keep the old coil packs in? These motors
despise any plug other than AC plugs, never use any other plug. I think the dealer showed you a normal to slightly abnormal amount of carbon build-up and wanted your money. But again....you are ahead of the game so don't take this the wrong way...I wish I had mine torn down to freshen it up just don't have the time.
Reason I ask is when you use the incorrect plug there is a chance you can stress the coil packs from too much resistance, unlikely but a chance. Seems this was isolated incidents but sudden.
If the BG44K didn't clean it up, then perhaps a valve lap may. This is just for others that may experience the same issues to try the 44K, it really works well.
Do you ever run the piss out of the motor? Meaning full-throttle accleration to the redline once or twice a tank? This will really help blow out excessive carbon. If you started getting multiple misfires after you were geting on the gas hard, you very well could have dislodged a piece of carbon under a valve and causing a compression leak, then no ignition. Looks like a cold or "cooler" cylinder at 2&5 and this would be the case under low or no combustion. The ECM could have adjusted for this not throwing a rich code....dunno.
What kind of fuel mileage were you getting? I wonder if this motor is running slightly rich, this would be relative to poor fuel mileage but just want to ask.
My gut tells me something else is amiss but you may have captured it with the head job. Hopefully anyway. You're going about this the correct way and replacing parts not to replicate the labor at a later date.
Current fuel is garbage, sitting in the tank for periods stated then running the motor which is rich until warm could have caused some build-up. Then the repeated starts and running cold. When you returned and ran the truck with the stale fuel you started getting problems. Current fuel is pretty much garbage after 3-4 months, will surely run but I know in small engines they wreak havoc.
I would drain the tank, drain the lines, replace the filter
BEFORE you turn the key and energize the fuel pump. Or at least disconect the fuel line and drain the tank via the pump if it can be done this way. How long was the fuel in the tank at the longest interval?
Best of luck, again....awesome job on the refresh and great pics.