Oil Pan and Pump removal and installation

Hey Joe,

Well, the new plugs didn't quite do it. There is less of a noticeable miss, but it still shudders somewhat accelerating from idle. Seems okay at speed. I'll need to go for a longer drive in better weather. Now a couple of things, which could be trouble. First as I mentioned before, the correct plugs have a roughly 1/4" shorter threaded end compared to the ones that were in there. That would suggest they extended further into the cylinder and what may have been why I had such trouble getting them out. Second, I probed the cylinder with an endoscope, and it was loaded with carbon deposits both on the top of the piston and especially the valves. I also noticed there was a relief on the edge of the piston which I didn't see in another cylinder or on a catalog photo. It doesn't look like it was from detonation, since it was too smooth and symmetrical. I also noticed what looks like a hole in the top of the piston, center, and at the edge of the recessed area. I couldn't get a clear image of it and even tried cranking the engine to attempt to get it into focus. I'm hoping it's just a speck of carbon, since there were no signs of any problems before all this. I was going to check the compression, but I can't get my gauge into that cylinder. It's one piece and I can't get it to turn. I'd have to make up some kind of adapter it I really need to do it.
The attached photos are of number 8-cylinder, piston and valves, I've included another cylinder to show the difference of the piston tops.

Hey Joe,

I struck out with getting a gauge, however I drove the truck for another 30 miles or so. It still ran bad. I took out the plug on number 8, which was the one that looked somewhat fouled, and I thought there was something not right with the piston. It looked fine. I put the scope in the cylinder again and it looked like some of the carbon was burned off the top of the piston and valve face, and I couldn't see anything that looked like a pinhole. I'm still puzzled by that edge cup on the edge of the piston though. I changed out the new IAC valve back to the original and it seems to idle a little higher and smoother than the replacement.
I reran the tests and still no codes. I'm looking at throwing in the towel. I can't think of anything that could have happened when I took off the upper manifold. Only the TPS sensor was exposed on the bench when I sprayed some cleaner into the manifold and let the crud drain out the PCV connection fitting.

Tony

I never sprayed the outside of the throttle body, but I did spray cleaner into and onto the throttle plates. But the manifold was upright. I don't see how I could have gotten the TPS wet. Besides, RPM increase is smooth with no fluctuations and since the "miss" is at all RPMs and not erratic wouldn't that mean fuel or spark? I don't know if this is a reliable test, but I put a timing light on all 8 wires and it was flashing. So I keep thinking fuel which means injector which means taking everything off again and pulling the injectors. I just can't figure how one would clog or partially clog while the engine sat for a few weeks. The fuel filter has probably less than 500 miles on it.
Anyway, thanks for all your help and advice. I know this was a long one. If I ever figure it out, I'll let you know.