My 95 crapped out on me on the highway last night. It started stumbling pretty badly under power. I got it off the freeway and to a motel, with some difficulty, where I was able to spend the night. It died on the way into the motel parking lot and would not start. This morning, it started, again ran like crap under load, but got as far as a gas station, where we swapped the fuel filter. (Doing that outside on a +5 F Minnesota morning is Not Recommended.) We also added a bottle of Heet and a bottle of injector cleaner. Once it got fuel back in the lines, it ran fine at idle and revving the engine in park, and then just long enough to get back on the freeway, where it went back to bucking and stumbling under any sort of load at all - except for one period of about a minute when it ran fine and got up to 70, with a change in the exhaust note. Then it ran like crap again.

I managed to limp along to the next town at 30-35 MPH; if I let it idle, or used just a very small amount of power, it'd run, but any load at all and it'd stumble badly. It did turn on the MIL. I barely made it up the hill into the next town, where I pulled in and filled it up - it'd used about a half a tank on the 80 miles since we set out the night before. As with last night, once it started running like crap, it also stumbled when revved up in neutral. Then it refused to start.

It's sitting there now, about 30 miles away from home. I fully expect it to start and run tomorrow morning when I get back to it, just like it did today.

The plan so far is to get back to it tomorrow, plug in the code scanner and see what that tells me, and then see if I can limp it to my mechanic.

Current guess is a plugged catalytic converter, based on the age of the truck (and 216K miles) and the change in the exhaust note when it ran well. Other guess is the O2 sensor or the injector spider. Any other thoughts?

 

Check to make sure that air is not entering the intake after the MAF sensor. Had that happen to me once when playing offroad and had the same symptoms you described.

Though, I'll put my money on your cat dieing on you.

 

Rap on the cat and listen for rattles and/or pull the O2 sensor in front of it (it'll be loud) and see if the anything changes.

 

Can I run it without the O2 sensor long enough to get it to my mechanic, if that makes it run right?

 

Might throw an SES light and be loud, but there should be no damage.

 

Sure sounds like thee ol EGR pintle issue gummed up.
Next i would go after the IAC,then check spark plug/wires.(Replace only with DELCO)
(..Possible water in gas?)

 

Plugs, wires, and distributor rotor and cap replaced about 5000 miles ago with AC Delco (except E3 plugs, and have run fine since then).

It had thrown a P0131 code, but that didn't return after driving it a bit. I got about 3 miles down the road toward my house and it quit. I threw up my hands and had it towed to a dealer. They're thinking injector spider, but not sure yet.

 

Turns out that I screwed things up when I cleaned the EGR back in July. They found a vacuum leak and a crossthreaded and bent bolt. They cleaned that all up, and it runs fine now.

I have no idea how it went 6 months and 8000 miles before failing...