For 1990-2009 cars

Checks | Actions
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DEFINITION: Fuel ignites in the intake manifold, or in the exhaust system, making loud popping noise.
Preliminary Checks |

• | Refer to Powertrain On Board Diagnostic (OBD) System Check .

• | Refer to Important Preliminary Checks.

• | Refer to Visual/Physical Checks.

• | Search for bulletins.

Sensor/System |

• | Check for the following intermittent ignition system conditions:

- | Intermittent CKP Sync or CKP 18X Signal

- | Intermittent ignition feed circuit or sensor ground circuit to the crankshaft position sensor or the camshaft position sensor

- | Intermittent 3X reference signal

- | Intermittent camshaft position signal

• | Check the throttle body inlet screen for foreign objects or damage that can affect the MAF sensor airflow sample.

Fuel System |

• | Check for incorrect fuel pressure.

- | Refer to Fuel System Pressure Test (VIN K) .

- | Refer to Fuel System Pressure Test (VIN 1) .

• | Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

• | Ensure each injector harness connector is connected to the correct injector.

Ignition System |

• | Check for proper ignition voltage output using the following steps:

- | Clip the J 26792 spark tester to engine ground.

- | Connect one end of a spark plug wire to the spark tester; leave the other end of the spark plug wire to the coil being tested.

- | Connect one end of another spark plug wire to the other coil tower; connect the other end of the spark plug wire to ground.

- | Crank the engine while observing the spark tester; a crisp blue spark should be observed.

- | Repeat the above steps for each coil.

• | If adequate spark is not present at the coils, check for the following conditions:

- | Coils - Cracks, carbon tracking/arcing, or a resistance value outside the specified range.

Coil Secondary Resistance
5000 - 8000 ohms (5K - 8K ohms)

- | Spark Plug wires - Signs of arcing/cross firing, cracks, carbon tracking, plug boot damage, pinched, incorrect routing, or a resistance value greater than the specified value.

VIN 1 Spark Plug Wires Resistance
3280 - 4921 ohms per meter (1000 - 1500 ohms per foot).

VIN K Spark Plug Wires Resistance
3280 - 4921 ohms per meter (1000 - 1500 ohms per foot).

| Important: Spraying the secondary ignition wires with a light mist of water may help locate an intermittent problem. Ignition components will arc to ground when a secondary component is malfunctioning.

- | Malfunctioning ignition control module.

- | Ignition System Wiring - Loose ignition module feed or ground connection, or damaged system wiring.

• | Remove spark plugs and check for the following conditions:

- | Fouled plugs

- | Cracks

- | Wear

- | Incorrect gap

- | Burned or damaged electrodes

- | Incorrect heat range

• | If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.

Engine Mechanical |

• | Check the engine for the following conditions:

- | Compression

- | Sticking or leaking valves

- | Worn camshaft lobes

- | Valve timing

- | Bent push rods

- | Worn rocker arms

- | Broken valve springs

- | Excessive oil in combustion chamber - Leaking valve seals. Refer to Oil Consumption Diagnosis .

- | Low cylinder compression. Refer to Engine Compression Test .

• | Inspect for the following incorrect engine parts:

- | Camshaft

- | Cylinder heads

- | Pistons, etc.

Additional Checks |

• | Check Intake and exhaust manifolds for casting flash.

• | Check TCC operation. Refer to Torque Converter Clutch Evaluation and Diagnosis .

• | Check the exhaust system for a possible restriction in one or more of the following areas:

- | Damaged or collapsed pipes in the exhaust system

- | Heat distress or possible internal failure of the muffler

- | Possible plugged Three-Way catalytic converter

• | Refer to Restricted Exhaust System Check .