This guide details the complete process of diagnosing and repairing a Volkswagen/Audi vehicle with a potential intake camshaft timing issue, often associated with the VCDS fault code 16684. This specific code indicates that the intake camshaft is not properly aligned with the crankshaft, potentially due to a jumped timing chain or worn components.
Identifying the Problem: VCDS 16684 and its Symptoms
The VCDS error code 16684 typically points to an “Intake Camshaft Position Sensor (G40) / Engine Speed Sensor (G28): Incorrect Correlation.” This signifies a discrepancy between the signals received from these two crucial sensors, often caused by a misaligned intake camshaft. Symptoms might include:
- Check Engine Light: The most obvious sign.
- Rough Idle: The engine might run unevenly or stumble at low RPMs.
- Poor Performance: Reduced power and acceleration.
- Misfires: The engine might misfire, leading to further performance issues.
- Increased Fuel Consumption: A noticeable drop in fuel economy.
Comprehensive Repair Procedure for a Misaligned Intake Camshaft
Addressing this issue requires a methodical approach. Here’s a step-by-step guide:
Preparation and Access:
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Service Position: Position the vehicle for optimal access by removing the front bumper cover and pulling the front end forward approximately 4 inches. This provides access to the crankshaft pulley.
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TDC Alignment: Rotate the crankshaft until it reaches Top Dead Center (TDC) on the compression stroke for cylinder 1. Verify this by aligning the timing mark on the exhaust camshaft with the corresponding mark on the cylinder head.
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Crankshaft Lock: Secure the crankshaft at TDC using a specialized crankshaft locking tool. This prevents accidental rotation during the repair process.
Camshaft Inspection and Component Removal:
- Intake Cam Inspection: Observe the intake camshaft timing mark. In this instance, it was found to be misaligned by one link on the timing chain.
- Cam Chain Tensioner (CCT): Attempt to install the CCT compressor tool. If the bottom has rotated, making threading impossible, loosen the CCT.
- Sensor and Bearing Removal: Remove the intake camshaft position sensor from the front of the engine. To gain better access to the CCT, remove the exhaust bearing located just below it.
- Intake Camshaft Removal: Completely loosen the intake camshaft bearing caps and remove them. Loosen the exhaust camshaft bearing caps as per manufacturer specifications, removing the rear four caps. This will provide the necessary clearance to remove the intake camshaft and CCT. Note: This step may require some maneuvering due to the limited space.
CCT and Chain Inspection:
- CCT Disassembly and Cleaning: Inspect the CCT for damage and remove any remnants of shredded chain guide shoes. Clean the CCT thoroughly.
- Chain Guide Shoe Replacement: If the guide shoes are damaged, replace them with new ones. Ensure proper seating by filing down the mating surfaces of the CCT if necessary. Use a rubber mallet to gently tap the new shoes into place.
Reassembly and Timing:
- CCT Seal Installation: Apply a small amount of gasket sealer to the metal seal under the CCT to prevent movement during reinstallation. Lightly tighten the CCT without the chain in place and allow the sealer to cure for an hour.
- Intake Camshaft Installation: Carefully reinstall the intake camshaft, ensuring proper alignment with the timing chain and CCT. This process requires patience and precision to achieve the correct link spacing. Verify 14 links between the camshaft timing marks (16 if counting the links above the markers).
- Bearing Cap Installation: Reinstall the bearing caps on both camshafts, gradually tightening them in a crisscross pattern with a torque wrench to manufacturer specifications.
Verification and Final Steps:
- Crank Rotation and Verification: Remove the crankshaft locking tool. Rotate the engine two full turns by hand to ensure smooth operation and proper camshaft timing.
- Reassembly: Reinstall all remaining components, including the valve cover, intake camshaft position sensor, and front end assembly.
- Engine Start and Testing: Start the engine and check for any fault codes using a VCDS scanner. Test drive the vehicle to confirm proper operation and listen for unusual noises.
Conclusion
Addressing a Vcds 16684 fault code requires meticulous attention to detail and adherence to proper procedures. This guide provides a comprehensive overview of the repair process. Always consult the vehicle’s specific repair manual for detailed torque specifications and procedures. While this guide offers valuable information, professional assistance is recommended for those unfamiliar with complex automotive repairs. A successful repair will restore the engine’s performance, fuel efficiency, and prevent further damage.
