DEFINITION: The engine continues to run after the key is turned to the OFF position, but runs very rough. If the engine runs smooth, check the ignition switch.

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

Fuel Injectors

Check the fuel injectors for fuel leakage.

Fuel System

Perform a fuel system operational test at the pressure test connector. Refer to Fuel System Diagnosis .

Exhaust Gas Recirculation (EGR)

EGR valve not opening - Refer to DTC P0401 , DTC P0404 and Exhaust Gas Recirculation Valve Replacement .

Intake manifold gaskets

Check for leaks.

Misfiring, cross firing or cutting out under load

Check for misfiring, cross firing or cutting out under load.

Spark Plugs

Check for wetness, improper gap, cracks, burned electrodes and heavy deposits.

Ignition Coil

Check ignition coil connections.

Ignition System

Check ignition system for moisture, dust, cracks, burns, etc. Spray plug wires with fine water mist to check for shorts.

Powertrain Control Module (PCM) and Ignition System

Check PCM and ignition system for faulty grounds.

Secondary Ignition Voltage Output

Check secondary ignition voltage output with the SA9199Z tester.

Engine Valve Timing and Compression

Check engine valve timing and compression.

Engine Parts

Check for worn or incorrect basic engine parts such as camshaft heads, pistons, rock arms, lifters, broken or worn valve springs, etc.