VW Lupo Diesel Timing Issues Slash Engine Performance

I had a very similar issue with my 2003 VW Polo diesel. I have some experience working on cars but mainly stick to basic maintenance. The symptoms you describe match exactly what I experienced, engine light permanently on, poor performance, and terrible fuel economy. The camshaft and crankshaft position values were also showing errors in diagnostics. After taking it to my regular workshop, they found the crankshaft sensor was faulty. These sensors monitor the position and rotational speed of the crankshaft, which is crucial for proper engine timing and fuel injection. When they fail, the engine management system cant optimize performance properly. The repair involved replacing the crankshaft sensor, which cost 340€ including parts and labor. After replacement, all issues cleared up immediately, engine light went off, power returned to normal, and fuel consumption improved. Before suggesting more specific advice, could you share: Current mileage on your Lupo? When was the timing belt last changed? Are there any additional warning lights besides the engine light? Does the engine run rough at idle? This information would help determine if your issue is indeed similar to what I experienced with the sensor.

Just had mine fixed last week after latest service. Same symptoms but turned out the cam sensor was the culprit, not the timing chain. The engine synchronization was completely off due to faulty sensor readings between the crankshaft and camshaft positions. Got it sorted for 280€ total, sensor replacement plus diagnostic time. Now running perfect again with proper power and normal fuel consumption. The engine management light cleared right after the repair. Worth noting that my timing belt service history is clean and current. Make sure they check both sensors during diagnosis since they work together for engine timing.

Thanks for sharing the outcome. I had suspected the cam sensor might be the issue too since we had such similar symptoms, but my workshop went straight for the crank sensor on my Polo based on their diagnostic readings. The engine synchronization being off due to incorrect position readings between crankshaft and camshaft is a common failure point on these engines. Good point about checking both sensors, they really do work as a pair to maintain proper timing and fuel injection control. Your repair cost was actually better than mine at 280€ versus the 340€ I paid. The reference value errors can be tricky to diagnose since both sensors feed data to the engine control unit for timing. At least these sensor issues are relatively straightforward fixes once properly identified. Glad to hear your timing belt maintenance was up to date. That at least ruled out more serious timing issues. Amazing how a small sensor can cause such significant performance problems when it starts sending incorrect signals.

Wanted to circle back and thank everyone for the input. Really helped confirm my suspicions about sensor issues. The cam sensor fix at 280€ resolved all my problems, no more engine light, misfire symptoms cleared up, and power is back to normal. The reference value errors between crankshaft and camshaft positions were exactly what caused my performance issues. Important learning was that proper diagnosis is key since these timing-related symptoms can come from either sensor. While timing belt maintenance is important, sensor failures are actually pretty common on these engines. For anyone searching with similar symptoms, get both sensors checked during diagnosis. The repair cost was reasonable considering how much it affected engine performance. Much better than continuing to drive with poor fuel economy and reduced power.