Symptom Troubleshooting Chart - Engine DRIVEABILITY: Backfires

BACKFIRES DESCRIPTION

PINPOINT TEST 8	BACKFIRES
DESCRIPTION	Sound produced from exhaust system

BACKFIRES - PINPOINT TEST REFERENCE

PINPOINT TEST 8		BACKFIRES
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 Perform PCM quick test. See PCM QUICK TEST . Are any DTCs displayed during continuous memory, key on engine off (KOEO) or key on 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 Remove the fuel pump fuse. Is strong blue spark visible at each disconnected high-tension lead while cranking engine?	Yes	Check spark plugs. See SPARK PLUG REMOVAL / INSTALLATION . If OK, Goto 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 PINPOINT TEST 10: FUEL LINE PRESSURE/FUEL PRESSURE HOLD INSPECTION . Fuel line pressure: 207-488 kPa (30-71 psi) for 3.0L/4.0L 240-380 kPa (35-55 psi) for 2.3L Is fuel pressure correct?	Yes	Go to next step.
4		No	If pressure is greater than 488 kPa (71 psi) for 3.0L/4.0L or 380 kPa (55 psi) for 2.3L: Replace fuel pump module. See FUEL PUMP REMOVAL / INSTALLATION . If pressure is less than 207 kPa (30 psi) for 3.0L/4.0L or 240 kPa (35 psi) for 2.3L: Check fuel supply line for restriction.
5	CHECK FUEL DELIVERY SYSTEM Check fuel pump fuel flow. See GENERAL PINPOINT TEST 9: FUEL PUMP INSPECTION . Does fuel system flow the required amount of fuel?	Yes	Check injector for leakage. See GENERAL PINPOINT TEST 11: FUEL INJECTOR INSPECTION . If injector leaks, service as necessary. If the injector is 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). See ENGINE COMPONENT TEST . Is a fault indicated?	Yes	Service as required.
6		No	Go to next step.
7	CHECK EXHAUST SYSTEM Perform engine vacuum test. See ENGINE COMPONENT TEST . Is there a restriction in the exhaust system?	Yes	Service as required.
7		No	Go to next step.
8	VERIFY TEST RESULTS Are test results OK?	Yes	Troubleshooting is complete.
8	VERIFY TEST RESULTS Are test results OK?	No	Service any additional symptoms. See SYMPTOM TROUBLESHOOTING CHART - ENGINE DRIVEABILITY .