Originally Posted by willwren
Soot that wipes off is rich fuel.
This may make perfect sense.
Here'* the score:
Started it up this morning to go get new spark plugs, and it was running smooth. Shut if off at the parts store, went inside and made my purchase. Upon returning and starting it up again, it was misfiring on #3, which is the same cylinder that was dead the other day (when the plug was black). I took it over to my buddy'* and we changed the plugs back to Autolite 605s, and I thought it would cure the misfire, but it didn't. We switched plug wires and then switched coil packs, and it kept misfiring on #3 the whole time. We still tuned the AFC to keep the LTFT from being so lean in the lower and middle ranges, but the misfire never went away.
So, we figure it could be a bad injector O-ring, a bad injector, a faulty injector driver, or something worse like a head gasket leak on #3. The interesting thing is that I experienced a few misfires before we did the cam & heads, but I never knew which cylinder it was on. Based on Bill'* info, the injector may be stuck on and over-fueling the cylinder, but I'll have to get a noid light to check it out. I haven't checked the oil level for a couple weeks, so after the car cools down I'll go take a look to see if it has lost any oil.
At this point I'm just a little frustrated with this thing. I hope I only need a new injector, or maybe just a clean-up job on my old ones. Let me know what you guys think.
I'll list AFC calibrations at a later time. I can't remember all of them at the moment. We didn't finish tuning the car, as it seemed silly to fine-tune it while it was misfiring.
Turn on your brains, boys and squirrels! Please ask for any details I've failed to include!