For 1990-2009 cars

### Engine Dieseling or Run-On

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.

Check the fuel injectors for fuel leakage.

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

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

• | Check the intake the manifold gaskets for leaks.

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

• | Check the spark plugs for wetness, improper gap, cracks, burned electrodes, and heavy deposits.

• | Check the ignition system for moisture, dust, cracks, burns, etc.

• | Check the engine valve timing and compression.

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