Engine Control System - 4.6L - Troubleshooting & Diagnosis: 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 mass air flow (MAF) sensor for proper installation, obstruction, contamination, and damage. Refer to Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor Replacement . Inspect the MAF sensor for proper seating of the connector and terminal. Test the manifold absolute pressure (MAP) sensor for proper installation, obstruction, and damage. Refer to Manifold Absolute Pressure (MAP) Sensor Replacement . Ensure the quality of the MAP sensor vacuum source. Monitor the knock sensor (KS) system for excessive spark retard activity.
Fuel System	Test the fuel system for correct operation, restriction, volume, and pressure. Refer to Fuel System Diagnosis . Test for proper operation of the fuel injectors. Refer to Fuel Injector Diagnosis . Test for fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis . Inspect the throttle body for coking. Refer to Throttle Body Service . Inspect for lean or rich conditions. Refer to DTC P0171, P0172, P0173 or P0174 Conditions for Running the DTC. Refer to DTC P0171 or P0172 or DTC P0174 or P0175 .
Ignition System	Inspect for proper ignition system operation. Refer to Electronic Ignition (EI) System Diagnosis . Inspect the spark plugs. Refer to Spark Plug Inspection . Inspect the spark plugs for correct application. Refer to Ignition System Specifications . Inspect for damaged ignition coils within the ignition coil module assemblies. Inspect for damaged or misaligned spark plug boots.
Engine Mechanical	Inspect the following conditions: Cylinder compression-Refer to Engine Compression Test . Sticking or leaking valve Worn camshaft lobes Valve timing Worn rocker arms-Refer to Valve Rocker Arms Cleaning and Inspection . Broken valve springs-Refer to Valve Spring Inspection and Measurement . Excessive oil in the combustion chamber-leaking valve seals Inspect for incorrect basic engine parts. Inspect the following: Camshaft Cylinder heads Pistons, etc.
Additional Inspections	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 . Inspect the intake and exhaust system for casting flash. Inspect the exhaust system for possible leaks and/or restrictions. Refer to Symptoms - Engine Exhaust .