The dreaded Vcds 16684 code often indicates a serious issue with your vehicle’s camshaft timing. This detailed guide walks through a successful repair process, offering valuable insights for tackling this complex problem. While this specific repair was performed on a Volkswagen/Audi (as evidenced by the use of VCDS), the principles and steps outlined can be helpful for understanding camshaft timing issues across various car makes and models.
Understanding the Problem: Camshaft Timing
Camshaft timing is crucial for engine performance and efficiency. When the timing is off, the engine’s valves don’t open and close at the correct moments, leading to poor performance, misfires, and potentially catastrophic engine damage. The VCDS 16684 code specifically points to an issue with the intake camshaft timing, signaling that it’s out of sync with the crankshaft.
The Repair Process: A Step-by-Step Guide
The repair involved a meticulous, step-by-step approach to ensure the camshaft timing was correctly restored.
Gaining Access
The front bumper cover was removed and the front end pulled forward to access the crankshaft and camshafts. This “service position” provided the necessary space to work comfortably.
Setting Top Dead Center (TDC)
The crankshaft was rotated to Top Dead Center (TDC) on the compression stroke for cylinder number one. This ensures the engine is in a known position for accurate timing adjustments. The alignment of the exhaust camshaft mark with the arrow on the cylinder head confirmed TDC. A crank locking tool was used to secure the crankshaft at TDC.
Identifying the Issue
Upon inspection, the intake camshaft was found to be off by one link on the timing chain. This misalignment was the root cause of the VCDS 16684 code.
Addressing the Cam Chain Tensioner (CCT)
Accessing and removing the CCT proved challenging. The bottom portion had rotated, preventing the use of the compressor tool. After loosening the CCT and removing surrounding components like the intake camshaft sensor and an exhaust bearing, the intake camshaft bearing caps were removed to further facilitate access.
Removing the Camshaft and CCT
Despite the previous steps, removing the intake camshaft and CCT remained difficult. Loosening the exhaust camshaft bearings provided the necessary clearance for removal. Inspection revealed that both CCT shoes were missing, likely contributing to the timing issue. Replacement shoes were installed in the CCT after cleaning and preparing the mating surfaces. A small amount of gasket sealer was used on the CCT seal to prevent movement during reinstallation.
Reinstalling Components
The intake camshaft, timing chain, and CCT were carefully reinstalled, ensuring the proper link spacing (14 links between camshafts, 16 including the timing marks). Bearing caps were torqued down incrementally in a specific sequence to ensure proper seating.
Verification and Final Steps
The crankshaft was rotated two full turns to verify the timing and ensure no interference. All camshaft-related bolts were double-checked for correct torque. The valve cover, gasket, and intake camshaft timing sensor were reinstalled. After reassembling the front end, the engine started without any codes. Test drives confirmed the successful repair, with the engine running smoothly and quietly.
Conclusion
Addressing the VCDS 16684 code requires a thorough understanding of camshaft timing principles and a systematic approach to diagnosis and repair. This guide provides valuable insights into the process, highlighting the importance of precision and attention to detail when working with critical engine components. While challenging, successfully resolving this issue can prevent further engine damage and restore optimal performance.
