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

• Check:
  • EGR for valve not opening - refer to EGR valve Codes P0401 or P1404 and EGR valve replacement in the "Engine Controls" section of this manual. See FAULT ISOLATION article.
  • 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 coil connections.
  • Ignition system for moisture, dust, cracks, burns, etc. Spray plug wires with fine water mist to check for shorts.
  • PCM and ignition system for faulty grounds.
  • Secondary ignition voltage output with service tool SA9199Z tester.
  • Check engine valve timing and compression.
  • Check for worn or incorrect basic engine parts such as camshaft(s) heads, pistons, rock arms, lifters, broken or worn valve springs, etc.