2015 Chevrolet Equinox L4 2.4L– Backfire

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The 2015 Chevrolet Equinox L4 2.4L may experience a "Backfire" symptom, where combustion occurs outside the engine's combustion chamber, often resulting in a loud popping noise from the intake or exhaust system. This condition may indicate timing issues, a lean air-fuel mixture, or ignition or valve system malfunctions. Proper diagnosis through a systematic approach, as outlined in the following procedure, can identify and address the root cause, restoring smooth engine operation and preventing further damage to components.

Procedure

1. Inspect the fuel system for the following issues:

• Fuel system operates incorrectly.
• Fuel pressure is incorrect.
• Fuel is contaminated.

2. Inspect the ignition system for the following issues:

• Spark plug gap is out of the specification range; abnormal; fouled by coolant or oil.
• Secondary ignition system is contaminated by moisture.
• Weak spark.

3. Check for leaks, splits, and kinks in the air induction and vacuum system. Note: the Throttle or Idle Learn must be performed after correcting any issues.

4. Inspect the Transmission Torque Converter Clutch (TCC) operation by activating the TCC ON using a Scan Tool.

• Expectation: Engine speed drops.

5. Inspect the Air Conditioner compressor operation.

6. Start and idle the engine, press the accelerator pedal, and inspect the response of the Heated Oxygen Sensor (HO2S).

• Expectation: HO2S response is quick.

7. Inspect for water intrusion in the HO2S connector.

8. Inspect the Mass Airflow Sensor installation; make sure the arrows on the sensor point toward the engine.

9. Inspect for leaks between the oil and fuel.

10. Use the Scan Tool to check the Knock Retard Parameter ID (PID) value.

• Expectation: equal to 0⁰.

11. Inspect the electromagnetic interface by suddenly pressing the accelerator pedal and monitoring the change in engine speed.

• Expectation: Large change in engine speed.
• Note: Inspect the high-voltage components near the ignition coils when the electromagnetic interface is present.

12. Use the Scan Tool to monitor the value of the Crankshaft Position Resync Counter PID.

• Expectation: Remains at 0 during all operating conditions and when moving the harnesses and connectors between the Crankshaft Position Sensor (CKP) and the Engine Control Module (ECM).

13. Inspect the Evaporate Emission Canister Purge Valve for a “stuck open” condition.

14. Inspect the Crankcase Ventilation operation.

15. Inspect the engine cooling system for the following issues:

• Thermostat heat range is incorrect.
• Engine Coolant level is incorrect.

16. Inspect the exhaust system components for the following issues:

• Physical damage and/or internal failure
• Catalytic Converter is restricted.

17. Inspect the engine components for the following issues:

• Excessive il consumption
• Oil leaks in the combustion chamber
• Cylinder compression is incorrect
• Valves are sticking or leak
• Camshaft lobes and rocker's arm are worn
• Valve spring is broken
• Excessive carbon build-up in the combustion chamber
• Part number is incorrect.

Conclusion

Understanding and addressing a "Backfires" issue requires a systematic approach to pinpoint the underlying cause. This guide provides a comprehensive diagnostic framework to help you identify and resolve the root cause efficiently, ensuring your 2015 Chevrolet Equinox L4 2.4L operates reliably and without unnecessary downtime.

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