mild but not tolerable sputter when accelerating

Recently purchased a 1992 rodeo, 3.1 5 spd, 180k miles. Knew it needed work when I bought it, great deal, needed a rig for my 16 year old to drive.
Repaired engine oil leak, intake manifold, distributor or both.
Replaced fuel filter, rebuilt throttle body unit, full tune up, cap, rotors, wires, and O2 sensor.
Found timing WAY out, reset after I figured out which harness to disconnect to circumvent the computer advance. Had the emissions tested when I couldn't get it to run right, passed with flying colors. Considering the mileage, I was very surprised. Compression test was 120 psi low, 130 psi high. Again surprised, suspect not original engine? No emissions sticker under hood, more to wonder about.
Problem is, when you accelerate, you can feel it stumbles and is running poorly. It improves if you STAND on the throttle, but doesn't disappear. I have tested the throttle position sensor and the MAP. Found the plug in for the PCM behind the "kick plate" and checked for any engine codes, none found, check engine light is good. The fuel pump has good pressure, although I'm wondering if it is too HIGH? My assumption is if the inputs and outputs are working OK, the computer shouldn't let it overfeed fuel. Could this be a computer problem?
ANY help or input would be much appreciated, almost at the end of my rope. Hate to take it to a shop and have them start swapping parts at my expense till they "find" the problem.

It could be due to old and tired injectors. It might be worth a couple tanks of gas with cheveron techron concentrate (costs like 8 bucks a bottle).

Has the timing *chain* ever been changed - that you know of?

I had a '91 Rodeo, same 3.1L GM engine as your '92, when we traded it at around 160k or so, it was in need of a new timing chain; typically good for 150-170k or so.

But, 180k+ might be pushing it.

Also, how's the cat convertor?

It's VERY possible that that engine is original; I never had a doubt in my mind that my '91 Rodeo couldn't have gone another 160K+ easily - just needed a new chain and a few other parts.

Also, fwiw, my current '97 Rodeo was in a front-end collision 4yrs ago, I no longer have an emissions sticker on my hood either. Engine was completely untouched in the accident, however, hood is 6yrs younger then the rest of the truck.

Has the timing *chain* ever been changed - that you know of?

I had a '91 Rodeo, same 3.1L GM engine as your '92, when we traded it at around 160k or so, it was in need of a new timing chain; typically good for 150-170k or so.

But, 180k+ might be pushing it.

Also, how's the cat convertor?

It's VERY possible that that engine is original; I never had a doubt in my mind that my '91 Rodeo couldn't have gone another 160K+ easily - just needed a new chain and a few other parts.

Also, fwiw, my current '97 Rodeo was in a front-end collision 4yrs ago, I no longer have an emissions sticker on my hood either. Engine was completely untouched in the accident, however, hood is 6yrs younger then the rest of the truck.

Thanks for the info, I am not really familiar with what symptoms a worn timing chain would cause. Is there any others that you know of?

When I had the intake and valve covers off, I set no 1 into timing position so installation of the distributor would be easier. When I turned it, I did feel some play between the crank and the cam. I don't know what is acceptable or normal tho. If you can feel the play, is that a dead giveaway that it is too badly worn?
Incidentally I did have the cat converter checked, it was clear.
I get the impression you like these rigs, I have to admit I really never gave them a second thought until this one came up and I took it for a spin. They really seem to be sturdy and fun to drive. Where you've had both the 3.1 and the 3.2, the factory specs the 3.1 at 120 hp, while the 3.2 is rated at 175. Does this sound about right? How do they both compare for MPG?

Thanks again for your help.
Harold

Nope, that 3.1L GM should be putting out roughly 140hp, IIRC - it's been a while.

My mpg were always a bit less in the 3.1L versus the 3.2L, mainly because the engines were hauling the same amount of weight, but my '97 3.2L puts out 190hp - not a lot different but believe me, there *was* a very noticeable seat of the pants difference.

I'd say, in her younger years, the 3.1L averaged 17-19mpg respectively; as she got over the 140k mark, I'd say that dropped to about 14-15mpg or so - but to be fair, she definitely, by 150k miles was nearing close to needing a new timing chain. This will effect timing, which effects everything in the overall scheme of power and efficiency.

The 3.2L, when new and up til I put 32" tires on her, got on average 19-22mpg city/21-24mpg on the highway; now that it's up to 170k now, with 32" tires and extra body accessories, I average about 17-19mpg city.

Yes, I've loved both my Rodeo's - I still regret having traded the '91 Rodeo; but we needed a fullsize truck to carry our camper and the '97 Rodeo's power and options were above what the '91 had to offer. But she was a damn good truck, I miss her.