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1997 Isuzu Hombre p/u accellerates rough

I call this my mult cultural truck because it’s American product, a Japenese make, and an Hispanic model. Really, it’s just a cheap imposter of an S-10.

Anyway, the truck idles smoothly. I can step on the gas when it is out of gear and the RPM’s smoothly go up.

However, when I put the truck in any gear, especially the higher gears, the accelleration gets rough and slow. It feels kind of like a miss, but like I said, it doesn’t do it in neutral or with the cluch depressed.

Here’s a brief history:

I bought the truck with under 70,000 miles from a small time dealer. I drove immediately to the License Branch from the lot and when I was driving away, I started hearing a strange clatter. It turned out to be the signal to change the timing chain. I also put two oxygen sensors in the truck as well.

About four weeks later, the clutch master and slave died and I replaced that.

About another six weeks later, the fuel pump stopped working.

About three months later, the check engine light came on and that turned out to be intermittent loss of connection with the wire plugs in the firewall (I lost all conductivity-- I think the dealer got a bit over zealous with the power blaster under the hood). I cleaned all those and put some electrolitic compound on the plugs.

The problem with accelleration came shortly after that. Periodically, the check engine light comes on (of course, by that time, I was perfectly content to ignore it).

I don’t have access to engine diagnostic tools anymore so I can’t plug it in anywhere either.

If anyone has any advice, I would greatly appreciate it.


You have decided to ignore your best clue to dealing with the problem. Go to any big chain auto parts store and ask them to pull the codes for you. Most of them will for free. Then post the code (actual code, not what anyone says about it). Note that if the light is on and off you need to do this when it is on.

So now it is shooting in the dark. First it would be good if you mentioned the basics - how old is that fuel filter? Accel problems are commonly from fuel starving. It might not show in neutral b/c the engine isn’t really under load. The same can come from a restricted intake - how old is the air filter?

I would also not assume that the problem with the wires is fixed - what wires are you talking about anyway? And how old are the plugs and spark plug wires?

The filter/pump assembly was replaced about 15k mi ago. The wires I was talking about are the ones that plug into the firewall. I bought the truck from a “good old country boy” (you can substitute your own derogetory phrase there) with a power washer. While I had the truck in pieces, I replaced the plugs and wires, too. All the work I did no the truck occurred between 70k and 90k when I just got fed up fixing it.

The rough accelleration is only at midrange rpm’s and seems consitent in all gears. Otherwise, I’d concurr with you about the filter I just replaced.

His “mechanic” I think even tried to fix a leak in the clutch slave cylinder by seperating the tranny/block and placing a thin gasket between them at the bottom. Oh, If I forgot to mention, I had to replace the throwout bearing, maybe from the stress of having the tranny at a slight angle from the gasket wedged in there?

I’ll check about the auto store. My dad was a mechanic for a fleet of utility vehicles so he always got a pretty good discount at NAPA. They don’t have diagnostic tools. Even though he died a few years ago, this is a small town and the manager still gives me the discount so I have never bought parts anywhere else.

Oh, how I long for old trucks with points and enough room under the hood to have a picnic.

Thanks a bunch. I’ll try to get codes tomorrow.

Did you have the same problems after you changed the fuel pump and filter as you had before you changed them?
I don’t want to even ask whether you measured the fuel pressure (at idle and under load), whether you measured the vacuum (at idle and at various rpm). I don’t want to even advise you to do so now. Neither, do I want to advise you to use a multimeter to check the ignition primary (and secondary wiring). Nor, advise you to get the repair manual for the instructions it contains. I don’t want to advise you to do anything which you haven’t done (or, stated doing)…even if it might help to diagnose the problems. Why not? You tell me----have you?--------and, would you?

Me again.

Thanks to those who have given advice.

I went to the Advance and their pocket computer came up with codes:
P0172- Fuel system too rich
P0300- Intermittent misfire bank 1

The gentlemen at Advance suggested the fuel system is too rich because unburned gas is being emitted from the misfire. They suggested I get new coil packs.

It sounds plausible to me but I wanted to find out if anyone has had any such experience. Hellokit advised me to check the the ignition with a multimeter.

Does anyone have any suggestions on how to do that? Although I never got more than the mildest of jolts from an old spark plug wire, I have heard the ignition can really throw you. I seem to remember people wiring Model T coils to cars way before alarms as anti theft devices.

So please, aside from telling me not to take the spark plug wire off and holding it while it is running, if anyone knows any “Whatever you do, don’t do…” Please tell me.

And next, what readings should I shoot for or where can I get specs for what the coils should put out?

Thanks so much.

I still wish I had an old truck with points, a distributor, and enough room under the hood to have a picnic.

To figure out how to check the coil pack you can go to Autozone’s website and use their online repair manuals. You never said if you had a 4 or 6 cyl so I can’t give you the specific link. The basic check is as simple as checking resistance between towers and doesn’t involve knocking yourself on your butt. While you’re add it check the resistance on your wires - you’ll find the specs for that in the Autozone manual too.

I believe that provides just a basic check and that a full one requires really fancy and expensive equipment at a shop. I do know that if the resistances aren’t w/in spec you should replace the coil. But I’ll assume that the resistance could check out and the coil could still be bad. At least you’ll have somewhere to start.

You could also swap that #1 injector with another - if the misfire moves with the injector you’ll know to replace the injector rather than the coil.

Thanks for the advice. For the record, it’s a 4 cylinder. I looked at the Autozone website and I feel pretty confident with the instructions.

As far as swapping injectors, it was a random misfire bank one. I only have one bank so I cannot even narrow down which is misfiring.

I did read something about GM injectors of the type in my truck causing similar problems though. GM even issued a bulletin about it. I guess, from what I read in another forumn, that the injectors get gummed up from additives and ethanol. I live in the Midwest so ethanol is unavoidable too.

Any experience with this?


Diagnosing from symptoms, alone, is practically impossible. Actual checks and tests need to be performed. Still, sometimes, it’s quicker, and cheaper, to replace an inexpensive part than to check/test for its proper operation. Sometimes.
If the spark plug wires are original, or otherwise in question, it’s best to replace them.
Spark plug wire are part of the “secondary ignition” (or, the actual “spark part”).
The primary part of the ignition needs to be checked-----with a multimeter. Visual inspection is inadequate. To do the checks, you need some kind of technical instructions.
Inexpensive spark test lamps, which are held, or clamp to the spark plug wires, can be used to visually determine if a spark plug is misfiring during idle.
Take care of the question of spark first, before concentrating on the fuel injectors.