This truck has the 4.3L V6. It runs and starts fine. It diesels when you turn the motor off. Sometimes you have to put in gear and turn it off to get it to stop. Occasionally when you are driving it there is a loss of power and it will misfire and it has even stalled. Gauges read normal when this occurs. Timing has been checked and is set correctly. Distributor cap and coil have been replaced. No water in the oil. Any idea what is causing this intermittent problem?