A tuned car with approximately 38,000 miles began experiencing a rough idle and shuddering after a brief drive and short park. The car started roughly and the issue worsened at subsequent stops. Turning the car off and on, and resetting to Map 0 did not resolve the problem. A service engine soon light illuminated, but the onboard computer (OBC) indicated no issues. A scan tool revealed a cylinder 6 misfire, a recurring issue previously resolved by restarting the car. No fuel pump codes were detected by the scan tool.
Using a Scan Tool to Pinpoint the Problem
A scan tool, like the Bav Scan Tool used in this case, is crucial for diagnosing car problems, especially intermittent issues like shuddering. While the OBC might not display specific errors, a scan tool can delve deeper into the engine control unit (ECU) and retrieve diagnostic trouble codes (DTCs). The cylinder 6 misfire code provides a starting point for troubleshooting. However, given the history of this code clearing with a restart, further investigation is necessary.
Common Causes of Engine Shuddering
Several potential causes can contribute to engine shuddering and rough idling:
- Spark Plugs: Worn or fouled spark plugs can cause misfires, leading to shuddering. Given the car’s mileage and performance tune, spark plug replacement is a likely solution.
- Ignition Coils: A faulty ignition coil can prevent the spark plug from firing correctly, resulting in a misfire. Testing or replacing the coil for cylinder 6 is recommended.
- Fuel Injectors: A clogged or malfunctioning fuel injector can disrupt the fuel-air mixture, causing a rough idle and shuddering. While no fuel pump codes were found, a faulty injector in cylinder 6 could be the culprit.
- Vacuum Leaks: A leak in the intake manifold or vacuum hoses can disrupt airflow and cause a rough idle.
- Other Potential Issues: Less common causes include problems with the mass airflow sensor (MAF), throttle position sensor (TPS), or even engine mounts.
Troubleshooting Steps
- Remove Aftermarket Tune: As the owner plans, removing the Procede tune is a vital first step. This isolates potential issues caused by the tune and allows for a clearer diagnosis.
- Inspect Spark Plugs: Visually inspect the spark plugs for wear, fouling, or damage. Replace them if necessary, especially if they haven’t been changed recently. Consider using OEM or equivalent high-quality plugs.
- Test Ignition Coil: Test the ignition coil for cylinder 6. A multimeter can be used to check for proper resistance. Replacing the coil is a straightforward procedure if it’s faulty.
- Check for Vacuum Leaks: Inspect vacuum hoses for cracks or damage. A smoke test can help pinpoint leaks in the intake manifold or other areas.
- Seek Professional Help: If the problem persists after these steps, it’s time to consult a qualified mechanic or dealership. They have access to more advanced diagnostic equipment and expertise to identify complex issues. While a dealership might not cover issues related to the tune, they can provide valuable insights.
Conclusion
A scan tool is an invaluable tool for evaluating engine shuddering and diagnosing car problems. While the cylinder 6 misfire code provides a clue, a systematic approach to troubleshooting is crucial. Removing the tune, inspecting spark plugs and ignition coils, and checking for vacuum leaks are good starting points. If the problem persists, seeking professional assistance is recommended to pinpoint the root cause and ensure proper repair.
