Detonation/Spark Knock/Pings

DETONATION / SPARK KNOCK
Definition: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with throttle opening.

IMPORTANT PRELIMINARY CHECKS
Before using this section you should have performed the "On-Board Diagnostic System Check" - Powertrain/On-Board Diagnostic System Check and determined that:
1. The control module and MIL (Service Engine Soon) are operating correctly.
2. There are no diagnostic trouble codes stored, or there is a diagnostic code but no MIL (Service Engine Soon).
^ Several of the following symptom procedures call for a careful visual/physical check. The importance of visual/physical checks cannot be over stressed. because they can lead to correcting a problem without further checks and can save valuable time.

VISUAL / PHYSICAL CHECK
This check should include:
^ Control module grounds for being clean, tight, and in their proper location.
^ Vacuum hoses for splits, kinks and proper connections, as shown on "Vehicle Emission Control Information" label Check thoroughly for any type of leak or restriction.
^ Air leaks at all mounting areas of the intake manifold sealing surfaces.
^ Ignition wires for cracking, hardness, proper routing, or carbon tracking.
^ Wiring for proper connections, pinches, and cuts.
^ The following symptom charts contain groups of possible causes for each symptom and cover several engines. These procedures are not necessarily meant to be done in consecutive order. If Tech 1 scan tool readings do not indicate the problems, then proceed in a logical order, easiest to check or most likely cause first. To determine if a particular system or component is used on a specific vehicle, refer to the "Electronic/Powertrain Control Module (ECM/PCM)" Wiring Diagrams for application. Electronic/Powertrain Control Module (ECM/PCM)

^ Make sure the customer has an actual problem.
^ If there is spray from only one injector on the TBI unit, there may be a malfunction in the injector assembly, or in the signal to the injector assembly. The malfunction can be isolated, by switching the injector connectors. If the problem remains with the original injector, after switching the connector, the injector is defective. Replace the injector If the problem moves with the injector connector, the problem is an improper signal in the injector circuits. Refer to "CHART A-3".
^ Trans Range (TR) pressure switch assembly operation. Transmission Range (TR) Pressure Switch Assembly Circuit Check

COOLING SYSTEM
^ CHECK: For obvious over heating problems.
^ CHECK: Low engine coolant.
^ CHECK: Loose water pump belt
^ CHECK: Restricted air flow to radiator, or restricted coolant flow.
^ CHECK: Faulty or incorrect thermostat.
^ CHECK: Correct coolant solution.

SENSOR
^ CHECK: Engine Coolant Temperature (ECT) sensor, which has shifted in value. Refer to "DTC 15 Diagnostic Aids". DTC 15

FUEL SYSTEM
^ CHECK: To determine if the condition is caused by a lean system, the vehicle should be driven at the speed of the complaint. Monitoring fuel trim will help identify the problem.
- Lean - Long term fuel trim greater than 150. Refer to "DTC 44 Diagnostic Aids". DTC 44

^ CHECK: Fuel pressure. Refer to "CHART A-6". Related Tests, Information and Procedures
^ CHECK: For poor fuel quality and proper octane rating.

^ If scan tool readings are normal and there are no engine mechanical faults, fill fuel tank with a premium gasoline that has a minimum octane rating of 92 and re-evaluate vehicle performance.

IGNITION SYSTEM
^ CHECK: Spark plugs for proper heat range and gap.
^ CHECK: Knock Sensor (KS) system operation.
^ CHECK: Ignition timing. Ignition Timing

ENGINE MECHANICAL
^ CHECK: For carbon build-up Remove carbon with top engine cleaner Follow instructions on can.
^ CHECK: For incorrect basic engine parts such as cam, heads, pistons, etc.

ADDITIONAL CHECKS
^ CHECK: Proper operation of EGR valve. Testing and Inspection
^ CHECK: Proper operation of air intake system.
^ CHECK: For proper transmission shift points.
^ CHECK: Torque Converter Clutch (TCC) operation.
^ CHECK: Service Bulletins for PROM updates.