EDIT 6-29-25 LONG SHORT THE PROBLEM WAS THE TANG ON THE NEW ROTOR HAD BROKEN OFF. I HAVE NO IDEA HOW IT RAN AT ALL.
94 3.9
The truck started loping like it was missing about halfway up the hill I always go up around the corner. Then as I turned off the road onto the flat it died. I tried restarting and it died right away. Checked the oil and the transmission fluid they were wet. Checked codes got a 62. This is a new to me computer a few years ago. I suspect that code is for whatever year it was on OE as the 94 does not have that option. EMR(Emissions Maintenance Required) miles not stored
After a few minutes it started and ran with me gassing it and I went back down the hill to the house. I tried to start it at the house and it has that acrid smell, I can't recall what it is. I've checked the fuel pressure and it went up to 25 key on and 35-40 when cranking.
I can't imagine what may have gone wrong. Have more than half tank of gas. I looked without getting down and there is nothing obvious in the tailpipe. It wants to run but something is holding it back and making it choke out like it is starving for fuel or something is stopping it rotating. I have the battery disconnected right now to let it erase itself. i guess I'll break out the MT2500 and start reading the manual again. Not sure I can do a lot with it of the motor doesn't run...Anything sound familiar???

 

OK the MT2500 tells me the battery is low. Would that cause this? I would think the alternator would keep it running once started. But I'm bad at electrical stuff.
It started ad idled for a couple minutes but I couldn't get any tests done.
I think the smell is the CAT. It is new (Walker) since I bought the truck and only put about 30K on it in the last ten years.

 

Clear codes, try and start it. See what codes come back.

 

It runs rough and dies. No new codes since I disconnected the battery.
I think I will disconnect the CAT and see how it runs, tomorrow when it is supposed to be cooler. I wonder would just removing the O2 sensor give it enough outlet to tell me if it is a restricted CAT?
The front of the CAT is discoloured. That sulphur smell also make me think that is the problem. It does burn oil so...

 

Just pulling the O2 sensor should be adequate to the task. Not sure which is easier though... If it's the original O2 sensor, they tend to 'become one' with the exhaust, and are a real pain to remove.

 

OK my brain is cooling off. The O2 sensor is relatively new.
If I find that the CAT is clogged. Never had that happen. What causes it and what do I need to do before I replace it.
I guess I'll look for oil in the plenum.
How do I tell if the heads are OK as far as seals etc letting oil get past?

 

What brand O2 sensor? NTK or Denso are the standards, Bosch sensors just don't seem to work very well in these trucks.

Need to see what your cat looks like. General failure is meltdown.... Usually from too much fuel.

How is your oil consumption? How do your plugs look? How many miles on it? Given we are in the first gen section, newest is gonna be what? 96?? So, minimum of 19 years old. Chances are REAL good the valve seals are dried out. They aren't bad to change, just tedious. (there are so many.....)

 

O2 is NTK and pretty new. It came out easy (7/8 wrench) It looks normal. It started up and ran. Made noise and loped a bit but did not try to die with the O2 sensor out. So CAT is probably the issue.

I just changed the oil, wires, plugs, coil cap & rotor. It had the normal amount of oil in it. A few months ago I checked it and it was low so I added a quart. That has been a rare thing. the CAT is a Walker 49 state about 10 years old. I did the whole exhaust from the Y back. The post I made when I decided the CAT was the problem then was in 2015.
The heads look like they are used replacements. I say so because they have writing on them in one of those markers they use a auto recycle places. It uses oil but not so much that I take notice or worry. Most reliable rig I have had aside from the 87 Jetta and the 97 Tacoma.

 

Probably wouldn't hurt to do valve seals then.... but, if you don't have excessive oil consumption, that's a job I would put off till another day.

Toss a test pipe in there, and see how it drives. Reset the computer though, having a clogged cat may have confused it some.

 

The clamp nuts loosened easily enough. I have the muffler off the back and it is loose in the front but the CAT will not come off. I can move it up and down and back and forth and it will turn about an 1/8 of a turn both ways with the big channel locks. But she won't even move an 1/8" to the rear!? I'm taking a break. If I get her off I figure the extra piece of pipe, about 2' they sent me with the kit I have in there will fit as a test pipe.
At least it is still cool this morning.