major loss of power..

If you're having issues with lack of power and idle more than likely the culprit lies somewhere with the fuel-injection system. Some items to check are the throttle-position sensor, airflow sensor, O2 sensor, EGR system and the ECM. If you have an Autozone nearby they advertise they'll hook a code-reader up and pull codes for free. Post the codes here or get yourself the Haynes or Isuzu workshop manual. Check for air-leaks as well in the induction areas.

The beauty of the 2.6L is it's simplicity and ruggedness. I miss my '88 LS as it was by far my favorite Trooper and is still running strong with its new owners and over 200K miles. I all I ever did besides regular maintenance was replace a water pump.

You might also want to adjust the valves and do a compression test to rule out problems in that area.

Steadily decreasing valve clearances due to valve recession/wear/non-adjustment could be the cause of a gradual decline in performance.

Typically the end results are burnt valves and loss of compression.

Thanks for the info. I replaced the muffler and ran through some "Lucas performance" fuel injector and upper cylinder cleaner and noticed a slight difference. I am going to check the valve clearance next. Also noticed that my auto-choke isn't working when i first start it. Thanks again for the info.

Thanks for the help everyone, but the culprit was the woodriff(?) key. I read about it in another post. The SOB was worn so bad and the insides of the timing gear and crankshaft pulley were notched out like you wouldn't believe. With those like that it was throwing off the timing so much that the truck would hardly run at all. So hopefully if anyone else reads this it will help them, check every little thing cause you never know. Isuzu's rule!!!!!