For 1990-2009 cars

#### Backfire

Checks | Action
--- | ---
DEFINITION: The fuel ignites in the intake manifold, or in the exhaust system, making a loud popping noise.
Preliminary Check |

• | Refer to Diagnostic System Check - Engine Controls .

• | Refer to Symptoms - Engine Controls .

Ignition System Checks |

• | Check for the proper secondary voltage output with a J 26792 spark tester, or an equivalent. Refer to Electronic Ignition (EI) System Diagnosis .

• | Inspect the spark plugs for correct operation and performance. Refer to Spark Plug Inspection .

Engine Mechanical Checks |

• | Check for any of the following engine mechanical problems:

- | Broken or weak valve springs

- | Low compression

- | Sticking or leaking valves

- | Incorrect valve timing

- | Incorrect or worn camshaft

• | Refer to Engine Compression Test in Engine Mechanical.

• | Check the intake and exhaust system for casting flash or other restrictions.

Additional Check | Check for a leaking or sticking exhaust gas recirculation (EGR).