My 1991 w150 has not run right in 5 years, I've had it to 4 shops and a dealer. I would say every sensor has been replaced and every system tested. The truck runs rich and fuel builds up in the oil. The truck is in great shape, has all its power and burns no oil. It acts as if the egr system is not working (rough idle,periodic loss of power and stalling) but all the egr components work fine. The shop I go to had it for a week and could not figure it out. I just realized that when the engine was right it would make a gear spinning noise, like a modular motor, when I would shut it off.(engine reset for the next start??) It no longer makes that noise and my not have since the problem began. (no codes) Can anyone help?

 

checked for clogged injectors.

 

Its a throttle body, both injectors have been replaced

 

Fuel pressure/regulator good.

 

checked/isolated the vapor/charcoal canister.

 

fuel pump pressure is good and the pressure regulator was replaced. I'd really like to find out what made that mod motor sound in the engine compartment when I shut the motor off.

 

I have checked the charcoal can in the past, but I will test it again.

 

possibly a solenoid or solenoids like the canister purge?

 

The voltage to the solenoid valves is normal, I used a stethiscope and heard the valves operate as I disconnected and then applied voltage, I did this a number of times.

 

How about the ecm itself.