Engine Dieseling Or Run-On

Engine continues to run after key is turned to the Off position, but runs very rough. If engine runs smooth, check ignition switch.

• Check fuel injectors for fuel leakage.

  Perform a fuel system operational test at the pressure test connector. Refer to FUEL SYSTEM DIAGNOSIS  .

  Fuel ignites in intake manifold or in exhaust system, making a loud popping sound.

• Check:
  • Intake manifold gaskets for leaks.
  • Misfiring, cross firing or cutting out under load.
  • Spark plugs. Check for wetness, improper gap, cracks, burned electrodes and heavy deposits.
  • Ignition system for moisture, dust, cracks, burns, etc.
  • Check engine valve timing and compression.
  • Check for worn or incorrect basic engine parts such as camshaft(s) heads, pistons, rocker arms, lifters, broken or worn valve springs, etc.