Troubleshooting misfires can be a complex process. This article details a real-world example of using VCDS for ignition coil testing and other diagnostic steps in a W12 engine. The owner suspected faulty ignition coils and used VCDS along with other methods to pinpoint the issue.
Several tests were conducted to isolate the cause of persistent misfires in cylinders 4, 9, and 11. Initially, a fuel pressure test ruled out leaks as the pressure consistently increased after engine shutdown. Following this, a Vcds Ignition Coil Test was performed by swapping coils between cylinders. However, the misfires remained in the same cylinders, eliminating the coils as the culprit. Similarly, swapping spark plugs also failed to resolve the issue, despite some plugs having wider-than-specified gaps. While a few misfires occurred in other cylinders during this test, the significantly higher misfire count in cylinders 4, 9, and 11 indicated the plugs were not the primary problem. These tests were conducted by making a change, reassembling the components, driving the vehicle, and then recording the misfire data using VCDS.
The conclusion so far points towards a problem isolated to cylinders 4, 9, and 11, primarily occurring at idle or low speed and low throttle conditions. Fuel injectors remain a possible cause, but accessing fuel injector data points within VCDS for this specific W12 engine proved challenging. The lack of readily available sensor data for fuel injectors in VCDS necessitates further investigation.
Next steps involve exploring whether specific injector data outputs are accessible within VCDS for this W12 engine. If such data isn’t available, physically removing and testing the injectors will be necessary. A compression or leakdown test would provide further insights, but specialized tools and in-depth knowledge of the W12 engine, as detailed in the Bentley service manual, are required for these procedures. Consultation with experienced Bentley mechanics is being pursued for further diagnostics and potential solutions.
