Symptom Definition

A mild to severe ping, usually worse during acceleration. Engine makes sharp metallic knocks which change with degree of acceleration.

Possible Causes & Corrections:

• Check for low engine coolant and correct coolant solution.
• Check for obvious overheating problems.
• Check for loose water pump belt.
• Check for restricted airflow to radiator or restricted coolant flow.
• Check for faulty or incorrect thermostat.
• Check for incorrect basic engine parts such as camshaft, cylinder heads and pistons.
• Check for plugged PCV system.
• Check transmission range pressure switch assembly operation.
• Check transmission shift pattern and downshift operation.
• Check TCC system for proper operation.
• Check spark plugs for proper heat range and gap.
• Check knock sensor system operation.
• Ensure initial timing is correct.
• Remove carbon from engine with top engine cleaner.
• Check for incorrect fuel pressure.
• Check for poor fuel quality and proper octane rating. If scan tester readings are normal and no engine mechanical faults are present, fill fuel tank with a premium fuel with a minimum octane rating of 92. Re-evaluate vehicle performance.
• Check for spray from one injector on TBI unit. Malfunction may be present in injector assembly or in signal to injector assembly. Isolate malfunction by switching injector connectors. If problem remains with original injector, injector is defective. If malfunction moves with injector connector, problem is an improper signal in injector circuits.
• Check for a shifted ECT sensor. See DIAGNOSTICS AIDS in DTC 15 chart in appropriate TESTS W/CODES article below.
• If emission test shows excessive NOx emissions, check all systems and components which could cause engine to run lean or too hot. See DTC 44 chart in appropriate TESTS W/CODES article.
• TESTS W/CODES - 2.2L
• TESTS W/CODES - 3.1L
• TESTS W/CODES - 3.8L
• TESTS W/CODES - 4.3L
• TESTS W/CODES - 5.0L
• TESTS W/CODES - 5.7L
• Check EGR valve for not working.
• Ensure correct PROM is installed in vehicle. Check dealer for latest application.