1990 Isuzu Other

I have a 1990 isuzu spacecab pickup 2.6l 4x4 5spd. Manual transmission. Rough idle sometimes wont stay running sluggish, loss of power. Massive gas usage. Changed plugs, fuel pump, filter screens on pump, vaccum lines still no change any thoughts?
May 11, 2007.

This sounds as if the computer is being told the engine is very cold. The computer gets the coolant temp from a separate sensor than the guage or light. If the sensor fails or you have an open circut, (broken wire) the computer adds fuel as if it is -40 degrees F. Find the sensor and check it. Other wise you might have the same problem with MAP sensor. 8)

May 12, 2007.
I have a '92 2.6L 4cyl 5spd Isuzu Spacecab with the same symptoms noted below. Through a two day series of inspections by my mechanic, it was found that there was a vacuum leak on the number 4 intake runner. The O2 sensor was malfunctioning, and truck was consuming gas similar to an 8 cylinder. In addition, the thermostat was also faulty. There was often no power, very sluggish, and often stalled out. The problem was diagnosed with a smoke test. The required repairs have led to the indefinite parking of this truck.

May 22, 2007.