VW Lupo Stalling Issues Point to Faulty Camshaft Sensor

Had very similar symptoms with a 2005 VW Polo 1.9 TDI. The engine would struggle to start, especially when cold, and would occasionally stall at intersections. The check engine light triggered due to inconsistent camshaft sensor readings. A proper diagnostic scan revealed the camshaft sensor was sending erratic signals. The real issue turned out to be more complex, the encoder wheel on the camshaft was damaged, affecting the sensor readings. The ignition timing was completely off because of this. The repair required removing the camshaft to replace both the encoder wheel and camshaft sensor. This was definitely not a DIY job, as it required precise timing belt alignment and specialized tools. The sensor failure symptoms can be misleading, while replacing just the sensor might seem like a quick fix, damaged encoder wheels often cause similar readings. Testing the camshaft sensor output with a proper diagnostic tool is crucial before replacing parts. Without proper diagnosis, you might replace the sensor unnecessarily when other components are actually causing the problem. This was a serious repair that required engine timing validation after completion. Would strongly recommend getting a full diagnostic scan before replacing any parts.

Thanks for sharing your experience. Very interested to hear about the encoder wheel being the root cause, as my car has those exact same symptoms, constant stalling and check engine light issues. The camshaft sensor readings on my Lupo were also all over the place. After getting it properly diagnosed, did the fix solve all your problems completely? Curious about the total repair cost for both the encoder wheel and sensor replacement, if you remember. Also wondering if any other related issues have popped up since the repair was done?

Can confirm the repairs completely resolved all those frustrating starting and stalling issues. The engine control system now works flawlessly since having both the encoder wheel and camshaft position sensor replaced. The repair cost came to 695€ total, which included realigning the timing belt and verifying proper ignition timing afterward. The camshaft sensor readings have been steady and reliable ever since the fix. No more check engine lights or problems with the crankshaft sensor coordination. Its been running smoothly for months now, with none of those original symptoms returning. Looking back, getting a proper diagnostic scan was crucial. While the failing camshaft sensor readings pointed us in the right direction, discovering the damaged encoder wheel as the root cause saved replacing parts unnecessarily. Having a skilled mechanic who understood the relationship between these components made all the difference. The investment was worth it for the peace of mind and reliable operation. No related issues have emerged since the repair was completed. The engine starts perfectly every time now, maintains steady idle, and performs exactly as it should.

After getting your detailed reply about the encoder wheel issue, I decided to take my Lupo to a reputable VW specialist. The diagnostic scan showed exactly what you described, both a faulty camshaft position sensor and damaged encoder wheel. The total repair came to 720€, slightly more than yours, but included a full timing belt service since they had to remove everything anyway. The mechanic showed me the old encoder wheel, which had visible wear marks causing the erratic sensor readings and engine misfire problems. Been driving for two weeks now and the difference is night and day. No more stalling issues, check engine light is off, and the engine starts perfectly every time. Really glad I got the proper diagnosis instead of just blindly replacing the sensor. The shop also validated all the engine timing after reassembly, which gave me good peace of mind. Thanks again for steering me in the right direction with this repair. Definitely saved me from throwing parts at the problem without fixing the real cause.