Check engine light stays on. The engine normally runs top-notch. No complaints whatsoever. Trying to get it to pass emissions, I got AutoZone to check the code: 0153. It indicated a faulty O2 sensor, so I replaced the sensor indicated. Unhooked the battery to clear codes, after driving a couple of days, CEL returned; test indicates 0153 again, and now it's starting to stall while under a load, while coasting, and once while idling, while I was looking for vacuum leaks. Any suggestions? I've been reading your posts and answers, and some of y'all seem extremely knowledgeable. Any tips will be appreciated. I've done a lot of work on this wonderful old truck, and I'd like to fix this myself.

Now I've found two thin tubes running to a spherical canister above the right front tire. They are black and white, and the white one was broken with discoloration making me think it was cracked for a long time before it broke. I've temporarily patched that tube. Can anyone tell me what that is and if it could be connected? I can't find it in my Haynes manual anywhere.

 

Went to pick up wife from work, and it stalled again, this time while rolling at 45-50 mph. When it stalls, it's like it just stops sending fuel. It shuts down exactly like running out, but when I stop and put it into park or neutral, it fires right back up again. Does that mean anything to anyone?

 

P0153 could be a wiring issue
And it is for Bank2 Sensor1 so Driver's side front O2 sensor, hope you changed the right sensor.

O2 sensor issue can not cause stalling, running rich or running lean yes, but engine would always run.
But a bad section of wiring harness could cause both issues.
So follow the drivers side O2 sensor wires up and into the harness and see if you can see any damage.

I would check or replace the Fuel Pump Relay, because of your comment about running out of gas feeling.
Fuel pump relay isn't a common problem but it does fail.
Near the Fuel Pump relay in the engine compartment power box, is the WOT(wide open throttle) relay, these are both the same part number, so you can just swap them.
WOT relay turns off A/C when you are at full throttle, so it isn't used alot, but should be replaced if that fixes the issue.

And as a bit of bad news, it could also be the fuel pump starting to go out...............
Usually you just go to start engine one day and pump is dead, but I have heard of intermittent operation prior to failure.

 

I switched the relays, as you suggested, and drove to the store and back without a stall. It's a pretty short piece of wire between the plug and the wiring harness, and I didn't find anything amiss. Nothing worn or cracked, that I could see. It's good to know that the stalling is most likely merely coincidental. So if it stalls again, I should look at the fuel pump? Thanks again.

 

Intermittent is always a tough nut to crack.
Until the intermittent part becomes inactive permanently it is just guess work.

1998 models have the Ignition Control Module(spark) built into the computer, which is actually more reliable than separate modules used in the past, but it also makes it tougher to troubleshoot a spark issues.
An overheating Coil Pack probably wouldn't restart right away.
So your first impression of a fuel related issue is most likely correct.

But unfortunately only time will tell with something like this.

Back to the P0153 code, I assume the correct O2 sensor was changed.
And the wiring and connector looks OK.
Do you hear an exhaust leak on the drivers side?
Exhaust leaks suck in air even though they also blow out exhaust, this can cause O2 sensor to change slowly, P0153 means that O2 sensor is not changing voltage as fast as it should.
O2 sensor generates its own voltage .1volts to .9volts is the expected range.
.45volts is the "sweet spot" the computer wants to see, this means the oxygen level in the exhaust, on that bank, is correct for a 14:1 air:fuel burn.
The voltage is floating based on oxygen content, it changes at least twice per second, so very fast.
Computer changes fuel injector timing slightly every time one opens then watches O2 response voltage to keep it "hovering" around the .45v sweet spot.

This is a chemical reaction generating the voltage and the chemical in the O2 sensor does eventually get depleted so voltage changing slows down, this would cause code P0153.
BUT.........corroded wire could cause voltage at computer to be stable, not changing much, oxygen coming in from exhaust leak could do the same thing, O2 reads oxygen only.

Because this is only on one Bank an upper intake vacuum leak or MAF sensor issue wouldn't make sense, that would effect both Banks.