I have a completely stock '99 which exhibits mis-fire/engine shudder under load. First noticed the problem while pulling a loaded trailer. When a downshift from O/D power seems to fall off; then when upshifting back into O/D a very bad shudder occurs. So bad that the front end visibly shakes. First thought was torque converter; reputable x-mission shop says no problem there.
Have had truck to repair shop and re-created the problem with OBD indicating mis-fires on Cylinders 2 and 7. (did not write the codes down). Check engine light comes on. Truck has 98k on it and no tune as of yet. Fuel pump was replaced @ 58k, allowed shop to tune-plugs, wires, fuel/air filters etc. Drove approx. 1k ok and started seeing the problem again.
Any Ideas??
Have had truck to repair shop and re-created the problem with OBD indicating mis-fires on Cylinders 2 and 7. (did not write the codes down). Check engine light comes on. Truck has 98k on it and no tune as of yet. Fuel pump was replaced @ 58k, allowed shop to tune-plugs, wires, fuel/air filters etc. Drove approx. 1k ok and started seeing the problem again.
Any Ideas??
