Engine Control System & Fuel System - 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 - Vehicle . Refer to Symptoms - Engine Controls .
Ignition System Checks	Check for the proper ignition coil output voltage with a J 26792 Spark Tester or equivalent. See Special Tools . Inspect the spark plugs for correct operation and good ignition system performance. Refer to Spark Plug Inspection . Inspect the ignition coil boots for damage.
Engine Mechanical Checks	Check for any of the following engine mechanical problems: Broken or weak valve springs Low compression Sticking or leaking valves Incorrect valve timing Incorrect or worn camshaft Refer to Engine Mechanical. See ENGINE MECHANICAL - 1.8L (LV6) Check the intake and the exhaust system for casting flash or other restrictions.