Engine Controls -- 4.6L (Troubleshooting & Diagnosis): Troubleshooting: Backfire

Backfire

Inspection/Test	Action
DEFINITION: Ignition occurs in the intake manifold, or in the exhaust system, making a loud popping noise.
Preliminary	Refer to Important Preliminary Checks Before Starting in Symptoms - Engine Controls . Search for bulletins.
Sensor/System	Inspect the following systems for proper operation: Exhaust gas recirculation (EGR) system - Refer to Exhaust Gas Recirculation (EGR) System Description Positive crankcase ventilation (PCV) system - Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical. Knock sensor (KS) system
Ignition System	Inspect for proper routing of the ignition control (IC) circuits in each ignition module assembly connector. Inspect the ignition coils for signs of carbon tracking or damage. Inspect for proper spark plug boot alignment. Inspect the spark plugs for proper heat range and reach.
Engine Cooling System	Inspect for proper engine coolant level. Refer to Loss of Coolant in Engine Cooling. Inspect the engine thermostat for proper operation or for the wrong heat range. Refer to Thermostat Diagnosis in Engine Cooling.
Engine Mechanical	Inspect the following conditions: Cylinder compression - Refer to Engine Compression Test in Engine Mechanical. Sticking or leaking valve Worn camshaft lobes Valve timing Worn rocker arms - Refer to Valve Rocker Arms Cleaning and Inspection in Engine Mechanical. Broken valve springs - Refer to Valve Spring Inspection and Measurement in Engine Mechanical. Excessive oil in the combustion chamber-leaking valve seals Inspect for incorrect basic engine parts. Inspect the following: Camshaft Cylinder heads Pistons, etc.
Additional	Inspect the vacuum hoses for splits, kinks, proper routing, proper connection, and fuel loading. Refer to the Emission Control Information label. Inspect the secondary air injection (AIR) check valves for proper operation. Inspect for proper operation of the torque converter clutch (TCC). Refer to Torque Converter Diagnosis Procedure in Automatic Transaxle. Inspect the exhaust system for possible leaks and/or restrictions.