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2006 VW Passat 2.0 FSI P2179 Fault: Rough Idle, Misfire, Knocking at Cold Start with OBD Errors

Model: 2006 VW Passat Fault Code: P2179 Posted: 2017-07-23 16:58

I own a 2006 Volkswagen Passat B6 2.0L FSI model. Recently, I've been experiencing persistent knocking and rough idle, especially during the first cold start. The engine starts at around 1200 RPM when cold, which is unusually high—this behavior persists even in winter. During a service visit, my technician identified issues with the NOx sensors (both upstream and downstream of the catalytic converter). The exhaust catalyst was found to be empty, so two upstream oxygen sensors were replaced. After this repair, the sensor-related errors disappeared. However, after 2500 km, new OBD errors appeared: P0300, P0302, and P0303 (indicating misfires in cylinders 1, 2, and 3). I replaced all spark plugs and tested the ignition coils—after these changes, the misfire codes temporarily resolved. However, new errors emerged: P2179, P2189, P0441, and P1020. I then replaced the fuel tank ventilation hose to address potential evaporative emissions issues. Currently, the car occasionally displays P0507 (idle air control issue) and P02179 (similar to P2179). The knocking is most noticeable during cold starts. When I inspect the newly installed spark plugs, cylinders 1 and 3 appear to be running in a rich fuel condition. I’ve observed that LTFT1 is within normal range, while LTFT2 reads at 25%. The intake manifold pressure is higher than expected. Opening the oil filler cap reveals significant airflow—this raises concern about potential vacuum leaks or improper sealing. The current OBD logs are available for reference: - Normal operation (no errors): https://drive.google.com/file/d/0B7m8Tl ... ZUV2c/view - Current condition with knocking: https://drive.google.com/file/d/0B7m8Tl ... VHN3M/view I am now seeing recurring P2179 and P0303 codes (misfire in cylinder 3). I'm seeking expert advice on how to diagnose and resolve this issue. Is a faulty PCV valve or vacuum leak likely? Could the high LTFT2 value indicate an underlying fuel delivery problem? I appreciate any insights from experienced VW Passat owners or mechanics.

Related fault codes
P2179
Comments (2)
Anonymous 2017-07-23 17:08

Check the engine oil for signs of fuel contamination as a precaution. A fuel-rich condition could be causing misfires and high LTFT2 values. Is LTFT2 at 25% positive or negative? This may indicate an over-rich mixture, possibly due to a faulty PCV valve or vacuum leak.

Anonymous 2017-07-23 17:13

Positive (+25%), this suggests a rich fuel condition. A high LTFT2 value combined with misfires in cylinders 1 and 3 points toward possible issues such as a failing PCV valve, intake manifold leak, or vacuum hose failure. These could cause both the rich mixture and knocking at idle.