For 1990-2009 cars

#### Backfire Symptom

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Definition: Fuel ignites in the intake manifold, or in the exhaust system, making loud popping noise.
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Perform a bulletin search.
2. If a bulletin that addresses the symptom is found, correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom?

--

Go to Step 11

Go to Step 3

3 | Perform the careful visual/physical checks as described at the start of Symptoms section. Was the visual/physical check performed? | -- | Go to Step 4 | Go to Important Preliminary Checks
4 |

1. Check for proper ignition coil output voltage with the spark plug jumper wires J 36012 and the spark tester J 26792.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 11

Go to Step 5

5 |

Notice: If spark plugs are gas or oil fouled, determime the cause of the fouling before replacing the spark plugs in order to avoid damage to the new spark plugs.

1. Remove the spark plugs and check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 11

Go to Step 6

6 |

1. Check the fuel pressure. Refer to Fuel System Diagnosis .
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 11

Go to Step 7

7 |

1. Perform the Fuel Injector Solenoid Coil Test and Fuel Injector Balance Test .
2. Replace any injector found malfunctioning.

Were any injector(s) replaced?

--

Go to Step 11

Go to Step 8

8 |

1. Check engine mechanical for the following conditions. Refer to Engine Mechanical for the diagnostic procedures.

• | Low compression.

• | Sticking or leaking valves.

• | Worn camshaft lobe(s).

• | Incorrect valve timing.

2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 11

Go to Step 9

9 |

1. Check the intake and exhaust manifold(s) for casting flash. Refer to Engine Mechanical .
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 11

Go to Step 10

10 |

1. Review all diagnostic procedures within this table.
2. If all procedures have been completed and no malfunctions have been found, review/inspect the following items:

• | Visual/physical inspection.

• | Scan tool data.

• | All electrical connections within a suspected circuit and/or system.

3. If a problem is found, repair as necessary.

Is the action complete?

--

Go to Step 11

--

11 | Operate vehicle within the conditions under which the original symptom was noted. Does the system now operate properly? | -- | System OK | Go to Step 2