Up 1.0L Starting Issues Point to Faulty Cam Sensor

Faced similar symptoms on a Polo 1.0 TSI. The engine misfires and hard starts pointed to sensor failure, but diagnostic testing revealed the encoder wheel on the camshaft was actually defective. The crankshaft sensor and camshaft sensors work together for proper ignition timing. When the encoder wheel deteriorates, it sends incorrect signals to the engine control unit, causing the exact symptoms described. The check engine light typically indicates this timing-related fault. The repair required removing the camshaft to replace the encoder wheel assembly. While not a common failure point, it is a known issue that can occur around 100000km. The job needs specialized tools and precise calibration to ensure proper engine timing after reassembly. This was a serious repair requiring careful attention to timing marks and proper torque specifications. A misaligned camshaft could cause major engine damage. Would recommend having a shop with proper diagnostic equipment verify the exact cause rather than just replacing sensors based on symptoms. The symptoms match what many mistake for a simple sensor problem, but testing the actual signal output helps identify if its the encoder wheel causing false readings.

Thanks for sharing that experience. Had nearly identical issues with my Up, rough idle, multiple start attempts, and persistent check engine light. I also initially thought it was just the camshaft sensor, but it turned out to be the encoder wheel like in your case. The engine control unit diagnostic confirmed faulty timing signals. After getting it properly fixed about 6 months ago, everything has been running smoothly. Would be helpful to know what repair costs you encountered and if youve had any related problems since the fix.

Had the encoder wheel replaced about 2 months ago and the car runs perfectly now. The camshaft position sensor was reading incorrectly due to the faulty encoder wheel, causing those ignition timing issues we both experienced. The total repair came to 695€ including parts and labor. Definitely worth fixing properly rather than just swapping sensors without proper diagnosis. The check engine light hasnt returned and cold starts are back to normal. The mechanic confirmed this is more common in these engines than a standalone camshaft sensor failure. The crankshaft sensor readings were fine, but the camshaft timing signals were erratic due to the worn encoder wheel. Important to have a proper diagnostic rather than guessing based on symptoms. No issues since the repair, the engine idles smoothly and starts reliably every time. The investment in getting the root cause fixed was better than trying cheaper temporary fixes.

After reading about similar issues, I took my car to a certified shop that specializes in VW group engines. The mechanic ran a complete sensor testing sequence and confirmed it was indeed the encoder wheel causing the camshaft position readings to be incorrect. The repair cost me 720€ total, which included the new encoder wheel, gaskets, and about 4 hours of labor. The car stalling issues disappeared completely after the fix. I learned the engine control unit was getting confused by the bad timing signals, which explained all those rough starts. It has been 3 months since the repair and no check engine light or starting problems have returned. While the bill was higher than just replacing sensors, fixing the actual problem saved me from potential engine damage. The shop showed me the worn encoder wheel and explained how it affects engine timing, definitely worth getting properly diagnosed rather than guessing at the issue.