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 Powertrain On Board Diagnostic (OBD) System Check .

• | Refer to Symptoms .

Ignition System Checks |

• | Check for the proper ignition coil output voltage with a J 26792 spark tester or equivalent.

• | Check the spark plugs for any of the following conditions:

- | Any wet or fuel fouled plugs

- | A terminal screw that is bent or loose

- | A ceramic insulator that has cracks, carbon tracking, or deposits

- | A tip insulator that has cracks, carbon tracking, deposits, or is loose

- | A center electrode that is loose

- | An incorrect spark plug gap

- | Any missing platinum pads

Engine Mechanical Checks |

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

- | Any broken or weak valve springs

- | A low compression

- | Any sticking or leaking valves

- | An incorrect valve timing

- | An incorrect or worn camshaft

- | Refer to Engine Mechanical.

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