Hi all,

Truck has run great since I've owned it until yesterday. Plugs were changed out with Autolites about 2 months ago.

Anyway, I was traveling to town about 15 miles away when it started sputtering about 3 miles into my trip. I immediately recognized it as a misfiring cylinder, so I stopped about halfway, opened the hood, immediately heard some arcing, and found it was arcing off the boot on the #4 cylinder. I had about 8 miles to the nearest parts store, so I drove the rest of the trip, purchased a new set of wires, and a couple of plugs. At this point there was no Check Engine light which I thought was odd.

As I was pulling the boot off the plug, I noticed the plug quite loose - about a full turn from getting blown out of the cylinder. I tightened up the plug, and replaced the plug wire for good measure. Truck seemed to run better while I ran a couple of errands in town, but as I was exiting town, it started to sputter a bit, then more, then it was a bad as it was before. The Check Engine light came on a couple of miles later, but since I was on my way home, and not so anxious to distance myself from home with a problem, I kept going. Subsequently, I don't know what my OBD code(s) is(are).

It was dark when I got home, so I waited until today to address it. Pulled the plug, and immediately noticed about 1/8" of the ground electrode was broken off with some metal buildup (melted on?) on the bend, and the center electrode was missing, and ever so little of the ceramic appeared to be chipped off. I replaced the plug with a new one. During my test drive, it drove fine for about half a mile, then slowly started to get worse until it was running as poorly as before about 3 miiles down the road. Drove it back home, pulled the plug, turned it over a few times, and it does appear to have good compression by sound only. Tested the spark through the plug, and it looks good. I can run the RPMs up high, and I can't discern any misfire, but it could just be the RPMs are too high. Under load, however, it doesn't matter what the RPMs are...the misfire is evident.

I'm guessing I missed the #4 cylinder when I torqued the plugs down after tightening them with a ratchet. I should have doubled checked.

As it stands now, I don't have a compression gauge to test the cylinder, and I'm not too keen on driving 15 miles to town with it running like this as I'd rather not risk damaging something if I haven't already. I will if I have to, but I thought I'd stop in here first to see if there are any ideas I can pursue.

Anyway...any ideas where to start doing some backyard troubleshooting?