For 1990-2009 cars

Checks | Actions
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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.