Symptom Troubleshooting - Engine (4 Of 5): Backfires

BACKFIRES DESCRIPTION

8	BACKFIRES
DESCRIPTION	Sound produced from exhaust system

DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	PRELIMINARY CHECKS Perform the following preliminary checks: Vacuum lines (check for damage and proper routing). Spark plug wire routing (proper firing order). Are all checks OK?	Yes	Go to next step.
1		No	Service as required. Verify symptom no longer exists.
2	PERFORM PCM QUICK TEST See PCM QUICK TEST . Are any DTCs displayed during Continuous Memory, Key ON, Engine OFF (KOEO), Engine OFF (KOEO) or Key ON, Engine OFF (KOEO), Engine Running (KOER) Self-Tests?	Yes	Check for cause. See DIAGNOSTIC TROUBLE CODE (DTC) INDEX - POWERTRAIN CONTROL MODULE (PCM) .
2		No	Go to next step.
3	CHECK SECONDARY IGNITION SYSTEM Is strong blue spark visible at each disconnected high-tension lead while cranking engine?	Yes	Check spark plugs. See IGNITION COIL-ON-PLUG AND SPARK PLUG - 2.3L or IGNITION COIL-ON-PLUG AND SPARK PLUG - 3.0L (4V) . If OK, Go to next step. If not OK, clean or replace spark plugs.
3		No	Go to next step.
4	CHECK FUEL DELIVERY SYSTEM Perform fuel pressure inspection. See TEST 9: FUEL LINE/FUEL PRESSURE HOLD INSPECTION . Fuel line pressure: 240 - 380 kPa (35 - 55 psi). Is fuel pressure correct?	Yes	Go to next step.
4		No	If pressure is greater than 380 kPa (55 psi): Replace fuel pump module. See FUEL PUMP MODULE . If pressure is less than 240 kPa (35 psi): Check fuel supply line for restriction.
5	CHECK FUEL DELIVERY SYSTEM Check fuel pump fuel flow. See TEST 8: FUEL PUMP INSPECTION . Did fuel system flow the required amount of fuel?	Yes	Check injector for leakage. See TEST 10: FUEL INJECTOR INSPECTION . If injector leaks, service as necessary. See FUEL INJECTORS . If injector OK, go to next step.
5		No	Check fuel supply line for restriction.
6	CHECK BASE ENGINE Check for base engine concerns (such as improper compression, worn camshaft/valve train, gasket leaks). Is a fault indicated?	Yes	Service as required.
6		No	Go to next step.
7	CHECK EXHAUST SYSTEM Is there a restriction in the exhaust system?	Yes	Service as required.
7		No	Go to next step.
8	Verify test results. If OK, See DIAGNOSTIC INDEX to service any additional symptoms.