Hi, I dont know if anyone can help me with this, it's kinda hard to explain. I have a 90 Trooper 2.6 5 speed, recently, it started to act up again, like it did before I replaced the O2 sensor. It's mostly noticable when I shift from 1st to 2nd gear, when I hit the gas it sputters, stumbles, and gets black smoke out of it. It idles rough, like it's missing. But I just replaced the plugs wires, cap and rotor not too long ago and the plugs aren't fowled or anything. IT sometimes runs ok cold, sometimes worse. I don't have a check engine light coming on, and all the vacuume lines are in place. Also, I used to get 20 to 21 mpg now I'm only getting 16, the milage was like this before I replaced the O2 sensor, and even though it ran better for a while, the gas milage never came back. Does anybody have any thoughts? <img src="/forums/images/graemlins/confused.gif" alt="" /> Could it be I bought a bad O2 sensor but the check engine light won't come on? And what could be making it pump out black smoke? Any thoughts would be really appreciated <img src="/forums/images/graemlins/kewl.gif" alt="" /> Thanks Dave <img src="/forums/images/graemlins/cheers.gif" alt="" />

Here is a shot out of the blue since something like this has happened on a friends car. My friend had that same type of problem and I forget exactly what it was, but he had the voltage wrong or something and it kept messing with the O2 sensor and pretty much made them bad after a few thousand miles.
Not to scare you because, I think it was a little more involed then your case. So a little more info for us, how many miles on the new 02. I honestly have no other ideas then that.

Sorry, I work nights, and just came home and started typing, kinda tired <img src="/forums/images/graemlins/sleeping.gif" alt="" /> I now have about 9000 miles on the new O2 sensor, I am going to try a new set a plugs and wires to see if it helps the miss situation, but the thing is, if you put on the A/C when the idle comensator cuts in , the idle smooths out, when it cuts out, it oges back to missing real bad. Today it seemed to do a little better, it still smokes from first to second gear <img src="/forums/images/graemlins/rolleyes.gif" alt="" /> but not all the time, and it doesn't sputter all the time. It's kinda weird how it sort of comes and goes all within one 25 mile drive home. I'm going to try another can of fuel injector cleaner and another tank of premium gas. I fiddled around with all the vacuume lines too, and nothing diffrent. If you have any other ideas please let me know, I'm getting to the end of my rope <img src="/forums/images/graemlins/frown.gif" alt="" />

Ok, I made a reply and it disappeared <img src="/forums/images/graemlins/confused.gif" alt="" /> Anyways, the O2 sensor has 9000 miles on it. It's still missing prety bad on an idle, although when you turn onthe A/C, when the idle compensator cuts in the idle smooths out, when it cuts off, it idles rough again, and now today it's not doing it as bad, it still smokes from first to second, but not every time, and it does'nt sputter every time either, today I'm going to try another can of fuel injector cleaner and a tank of premiun. If you have any other ideas please let me know, I'm at the end of my rope here <img src="/forums/images/graemlins/rolleyes.gif" alt="" /> I checked all the vacuume lines, pulled some out, replugged in and nothing new. Oh well

Black smoke is an indication of too much fuel, thus poor mileage. You might have a bad injector, which would cause one plug to become carboned up. Have you checked all of them? If one is black and sooty you likely have a bad injector. If they're all black the problem is something that affects the whole system. A fuel pressure regulator will sometimes leak into the vacuum line and the engine pulls fuel that way. A sticking regulator can cause the pressure to be too high. Regulators and injectors can be expensive so proceed carefully. And that's just the mechanical side, various sensors could be making the computer think it needs more fuel. Vehicle computers of that vintage were not as smart as they are now. Sensors had to be waaay out of range before they will set a code and turn your light on.

I'm sorry I don't have the magic bullet, but hope something here helps.

Thanks, it does help....Help me get depressed!!! <img src="/forums/images/graemlins/notooth.gif" alt="" /> No really, that is giving me a direction to go in, thanks for the info.

As the symptoms change!!!! <img src="/forums/images/graemlins/barf.gif" alt="" /> (Kinda sounds like a soap opera doesn't it???? <img src="/forums/images/graemlins/rolleyes.gif" alt="" /> Ok I'm pretty sure it got worse which is good. IT seems like it's missing all the time now, not just ona idle (ona???? <img src="/forums/images/graemlins/notooth.gif" alt="" /> must be a new term!!!) It misses when the A/C compressor cuts on, something it didn't seem to do before and on the road I can hear it and feel it under light throttle. A friend suggested that the cap might be cracked, even though it only has 10,000 miles on it. So, off to Advanced auto parts I go today (it's their grand opening, I figure I'll give them a run for their money and see just how much stuff they have in stock for Isuzus!!!) <img src="/forums/images/graemlins/grin.gif" alt="" /> I'll let you know what happens. But as far as the black smoke, I might still have an injector problem, or a sensor, so I might try an O2 sensor too while I'm at it. Thanks for all the suggestion!!! <img src="/forums/images/graemlins/kewl.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> Dave

My $0.02. Not really good news either. My 90 2.6 ran for 3-4 months with the O2 DISCONNECTED. Ran fine, 18 mpg. Ran so well I didn't know it was disconnected by the muffler shop that had accessed the exhaust manifold. I doubt the O2 sensor is your problem. good luck, stay with it.