Backfire. Pontiac Bonneville 2000

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 2000 🢒 Bonneville 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Backfire

Checks

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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 Before Starting in Symptoms .

•	Refer to Visual/Physical Checks in Symptoms .

•	Search for bulletins.

Sensor/System

•	Check for the following intermittent ignition system conditions:

-	Check for an intermittent CKP Sync or CKP 18X signal.

-	Check for an intermittent ignition feed circuit or sensor ground circuit to the crankshaft position sensor or the camshaft position sensor.

-	Check for an intermittent 3X reference signal.

-	Check for an intermittent camshaft position signal.

•	Check the throttle body inlet screen for foreign objects or damage that can affect the mass air flow (MAF) sensor airflow sample.

Fuel System

•	Check the fuel pressure. Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) or to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Outside 10-35 Degrees C (50-95 Degrees F) .

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

•	Ensure each injector harness connector is connected to the correct injector. Refer to Fuel Injector Electrical Harness Removal from Rail .

Ignition System

•	Check for proper ignition voltage output using the following procedure:

-	Clip the spark tester J 26792 to engine ground.

-	Connect one end of a spark plug wire to the spark tester. Leave the other end of the spark plug wire connected 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 spark should be observed.

-	Repeat the above steps for each coil.

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

Important:: If carbon tracking is detected on any component, replace that component and the component's mate.

-	Check the coils for cracks, carbon tracking or arcing, or a resistance value outside the specified range.

Coil Secondary Resistance
5,000-8,000 ohms

-	Check the spark plug wires for signs of arcing or cross-firing, cracks, carbon tracking, plug boot damage, pinched wiring, incorrect routing, or a resistance value more than the specified value.

Spark Plug Wire Resistance
3280-4921 ohms per meter (1000 ohms-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.

-	Check for a malfunctioning ignition control module.

-	Check the ignition system wiring for a loose ignition module feed or ground connection, or damaged system wiring.

•	Remove the spark plugs.

•	Inspect the spark plugs for the following conditions:

Fouling

Cracks

Important:: If carbon tracking is detected on any component, replace that component and the component's mate.

-	Check the spark plugs for signs of carbon tracking on the porcelain or arcing at the plug wire contact.

-	Check the spark plugs for incorrect gap. Refer to Maintenance Items in Maintenance and Lubrication.

-	Check the spark plugs for damaged electrodes.

-	Check the spark plugs for incorrect heat range. Refer to Maintenance Items in Maintenance and Lubrication.

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

Engine Mechanical

•	Check engine mechanical for the following:

-	Check the compression. Refer to Engine Compression Test in Engine Mechanical.

-	Check for sticking or leaking valves. Refer to Cylinder Leakage Test in Engine Mechanical.

-	Check for worn camshaft lobes.

-	Check for valve timing.

-	Check for bent push rods.

-	Check for worn rocker arms.

-	Check for broken valve springs.

-	Check for excessive oil in combustion chamber-Leaking valve seals.

•	Refer to Base Engine Misfire Diagnosis in Engine Mechanical for diagnostic procedures.

•	Inspect the following for incorrect basic engine parts:

-	Check the camshaft

-	Check the cylinder heads

-	Check the pistons, etc.

•	Refer to Engine Overhaul in Engine Mechanical for diagnosis procedures.

Additional Checks

•	Check intake and exhaust manifolds for casting flash. Refer to Intake Manifold Cleaning and Inspection in Engine Mechanical.

•	Check TCC operation. Refer to Torque Converter Diagnosis in Automatic Transaxle-4T65-E.

•	Check the exhaust system for a restriction.

-	Inspect the exhaust system for damaged or collapsed pipes.

-	Inspect the mufflers for heat distress or internal failure.

-	Check for a plugged 3-way catalytic converter. Refer to Restricted Exhaust System Check .