Isuzu SUV Forum banner
1 - 5 of 5 Posts

·
Registered
Joined
·
116 Posts
Discussion Starter · #1 ·
I read a lot of posts with various problems with the 3.2 and later motors, yet the 3.1 in my '92 Rodeo just keeps plugging along. I've chased a perpetual EGR issue, which never shows until we take a longer trip, but even then, it has never seemed to affect how it runs. Engine-wise, I've had to replace a few distributor caps and plug wires, a couple fan clutches, one Idle Air Control valve, thermostat and a few other minor things, and chased a few coolant and oil leaks, but it's never needed more than occasional topping off of fluids. Burns less than a quart of oil between changes. Only one O2 sensor, changed once. Pre-OBDII, so not much info for codes, but maybe also less to go wrong?

It has a timing chain, not a belt, still original at 140k. Throttle-body injection, pretty much conventional distributor and single spark coil, so no balky separate injectors or hi-tech ignition system to troubleshoot. Open the hood, you see the motor and an air cleaner like on my old '67 Ford Falcon, not all those glitzy add-on coverups and bulky intakes, hoses, wires and what-not. I get overwhelmed just looking at the pics of the newer engines! :shock:

It was pretty gutless since we've owned it, till I finally had to replace the old exhaust with a slightly upgraded one with free-flowing cat and muffler. It was like setting it free, it had a lot more power and snap ever since that one change from stock. It might be the lowest HP of the various sixes found in the Zu's, but it does the job for me.

The rest of the vehicle has been dependable as well, but it's getting worn out and rusty after 21 years of dirt, mud and snow. We've sunk far more money into keeping all that up than we ever put into the motor itself. Still, it's been very cheap to maintain, considering the years of use and abuse. Getting things diagnosed is another thing, nobody around here seems able to troubleshoot stuff and just wants to throw parts at it, so I do most all the wrenching myself, same as on my other rigs. That way, I know what's done and how well.

I just don't see much here on the ol' 3.1. What's other people's take?
-Ed
 

·
Registered
Joined
·
116 Posts
Discussion Starter · #8 ·
Great responses, thanks! I didn't know any of that myself. Really only that it was a GM motor, maybe built in Canada. I'll probably never do any of those swaps or upgrades, but very interesting nonetheless.

kg4miq, I'd be curious to hear any subjective or measured performance gains of your rebuilt 3.1.

I'm still used to gauging engine size by cubic inches, I was a bit surprised that the 2.8 is only 170 cu.in., the same size as the straight six that was in my 1967 Ford Falcon. The Falcon 170 with three-on-the-tree was real dog for performance, but steady and dependable with good gas mileage. Even the 3.4 is not much over 207 cu.in. and the 3.1 is quite small at 189 cu.in.

The 225 Dauntless V6 that was in my 1967 Jeepster is significantly larger, and I thought that was a pretty small mill, producing about 200 hp and 225 lb/ft torque. But with that long stroke, it could sure pull like a tractor and sounded like one too, lugging up a hill in second gear, which it could do all day without a hiccup. It still sounded good and ran great when I finally sold it, but the rest of the vehicle needed basically a frame-off resto and rebuild. Kinda like my Rodeo, except for the lugging tractor-pull part, lol!

-Ed
 

·
Registered
Joined
·
116 Posts
Discussion Starter · #10 ·
You could easily drop that much coin and more into a crate engine or shave a couple hundred off your cost if the rig already had the basically running 3.1.

I always knew the stock 3.1 was operating at far below its potential. Especially when I saw the improvement of better exhaust flow. I didn't even upgrade the throttle body's air filter from stock, which would let it breathe even better. Mine might not lug like a tractor, but it does love to rev! Maybe factory "undertuning" equates to engine longevity, or helps it to meet emissions, I dunno. I always thought a stronger-running motor would be more efficient, able to "loaf" more of the time instead of struggling to keep up with traffic or pull a hill. I'd generally have to floor it or shift down to get any chance at passing someone on the highway, for example. As a result, I often opted to slow down and stay behind someone, just because it took a forever stretch of clear road to safely pass, even on interstate.
 

·
Registered
Joined
·
116 Posts
Discussion Starter · #12 ·
Good real-world observations, Geoff. I guess my "stock" 3.1 bears out that low-compression, I never measured much over 160 pounds in compression tests, maybe closer to 130-odd pounds. I think I have some old tests written down somewhere. What's stock compression ratio? Something like 7:1? Yet the owner's manual suggested burning premium, though we usually burned regular anyway, but it sure did used to rattle the valves under load. Oddly, it quit doing that after the exhaust upgrade, or something else I'd done along the way with normal parts replacing/repairs.

Also as you noted, raw hp makes for a good advertising spec, but it doesn't mean much without a torque curve to match. The hp has to be there over a wide rpm range to really do any good, for us offroad types, higher hp at low rpm= :smile: !
 

·
Registered
Joined
·
116 Posts
Discussion Starter · #14 ·
Thanks, I was just being too lazy to go grab the owner's manual. I happened to be closer to it today :) so I looked it up. 8.5:1, the 2.6 is 8.3:1. According to Edmunds, it produced the same HP as the 26, a meek 120hp. Torque wasn't listed, but stated it had 30 more lb/ft than the 2.6. In '93, the new 3.2 made a stated 175hp, quite a bump up. http://www.edmunds.com/isuzu/rodeo/
Now I'm tired from all the exertion, and must rest. :lol:
-Ed
 
1 - 5 of 5 Posts
Top