Engine Control System - 2.5L (LE8) (Troubleshooting & Diagnosis): Troubleshooting: Backfire

Backfire

Checks	Action
DEFINITION: The fuel ignites in the intake manifold, or in the exhaust system, making a loud popping noise.
Preliminary Check	Refer to Diagnostic System Check - Engine Controls . Refer to Symptoms - Engine Controls .
Ignition System Checks	Check for adequate ignition coil voltage with a J 26792 Spark Tester or equivalent. Refer to Electronic Ignition (EI) System Diagnosis . Check for damaged or worn spark plugs. Refer to Spark Plug Inspection . Check for the correct ignition timing. Refer to Ignition System Timing Adjustment Procedure . Check for crossfire between cylinders. Check for the correct routing of the ignition coil electrical connectors.
Engine Mechanical Checks	Check for any of the following engine mechanical problems: Incorrect valve lash Broken or weak valve springs Low compression. Refer to Engine Compression Test in Engine Mechanical. Sticking or leaking valves Incorrect valve timing Worn or incorrect camshaft Refer to Symptoms - Engine Mechanical in Engine Mechanical. Check the intake and exhaust system for casting flash or other restrictions.
Additional Checks	Check for the proper fuel pressure. Refer to Fuel System Diagnosis . Verify the PCM grounds are clean, tight, and in the proper locations. Refer to Engine Controls Schematics . Check the Service Bulletins for any updates or information.