3 years later, and the same problem is back! Last time it got so bad, I took it to the dealer. They said a loose plug wire, and a cracked plug. I was just happy the problem was fixed. Now that it'* happening again, I'm thinking those two issues were results of the problem instead of causes. Again, it'* at part throttle, going up a grade, after it'* warmed up. Odd that it first happened in warm weather, and now in cold. I suppose the O2 sensor may have gone out again, due to the misfires. Perhaps the coil packs are giving fits, I've read here that they can read in spec, but still cause problems. I wouldn't think a fuel issue would go away for that long and return. Again, thanks for the wisdom!

Post #1 was added to https://www.gmforum.com/1992-1999-91...sfires-310539/ that was over 38 months old. Moved to a new thread and moved to Pontiac for visibility.

Glad to know how it came out last time!​​​​​​​

It is highly unusual to have this happen on this platform. What do you think would cause another broken plug and loose spark plug wire again?

How many miles on this car?

How many miles on this car when it had the previous issue?

Did they replace the other spark plugs at the same time as the broken one?

It has been three years, so any number of other things could be happening today completely unrelated to last time.

Plugged cat? Fuel pressure?
Misfires destroy cats not O2 sensors.

OK, after work today, I did my due diligence, and pulled each plug, examined closely for issues, and put back. Also pulled and reinstalled the plug wires from the coil packs. You never know if there might be some 'schmutz' in there! Test drove, and it seemed better, but still missing. Went to Autozone to see if any more codes, and there was, MAP sensor. I replaced it 3 years ago, and bought the lifetime warranty part. So, I got a new one free, and they even let me pop it in out in the parking lot! So far, no misfires, but I realize they may have killed the MAP sensor in the first place!
The car has 139K now, was probably low 120'* then. The plugs were AC Delco Iridiums, no more than a month old at the time. That was the first thing I did when the missing started then. It didn't make a noticeable difference, so I replaced the wires. I figured start with the obvious, as both looked like they were on for a while. This is the first post - 1995 car I've had long enough to do much more than basic maintenance on. A couple years back, the oil pressure sending unit blew, dumping all the oil! Thankfully my wife was right outside our neighborhood! Another time, the coolant elbow in the intake also blew, again close to home. This summer I replaced the starter, and Saturday I replaced the radiator hoses, which may have been original, they were super squishy! And it failed inspection because the serp belt was half shredded! I knew it needed changed soon, but not THAT day soon!!! So I've had relatively good luck with cars, my Dad was an ASE Master Mechanic in the '80s, and I feel like he'* looking out for us from the other side.

Glad that fixed it. That'* the good thing about lifetime parts. And the bad thing as well.

My wife drove it today, and said it did miss a little this morning, but not like before. I'm thinking coil packs, I haven't tested them, but have read they can read in spec, but still cause problems. I think the first time, I replaced the MAP sensor, and thought it was fixed, but then it got worse until I took it to the dealer.

Also, I just referenced Danthurs' coil test procedures, I'll dig out my meter and check them before I buy new.