Seat Toledo rough idle and starting issues

Sounds like a classic case of a failing camshaft sensor. The poor starting, stalling at idle, and check engine light are all consistent. Have you pulled the error codes? It could also be worthwhile checking the crankshaft sensor signal; a faulty crankshaft sensor can sometimes mimic camshaft sensor issues, as the engine control relies on both for proper ignition timing. An engine misfire could also trigger similar symptoms, but that would typically show up as a specific misfire code. Check the sensor wiring too, just to rule out simple issues.

Thanks for the quick reply. I did get a code – P0341, which points directly to the camshaft position sensor 'A' circuit range/performance (Bank 1 or single sensor). You mentioned checking the crankshaft sensor signal. What's the best way to do that without specialized equipment? And how can a faulty encoder wheel cause these problems?

P0341 pretty much confirms the camshaft sensor issue. As for the crankshaft sensor, without an oscilloscope, you're limited to visually inspecting the wiring and connector for damage. A multimeter might show if the sensor is completely dead (no signal), but it won't tell you about signal quality. The encoder wheel, being part of the camshaft, provides the timing signal to the sensor. If it's damaged or misaligned, the engine control receives incorrect information about the camshaft's position. This throws off the ignition timing and fuel injection, leading to poor running and stalling. Given the code and symptoms, it's likely either the sensor itself or a fault within the encoder wheel. I'd recommend getting it properly diagnosed by a workshop.

Appreciate the detailed explanation. I took it to a workshop, and you were spot on – the diagnostics pointed to a faulty camshaft encoder wheel. They replaced the camshaft sensor, and the total cost came to 695€. Runs like a charm now!