Seat Formentor Lean Running Issue

Lean running on a Formentor sounds familiar. I had similar symptoms: check engine light, rough idle, and power loss. Did you check the fuel injectors? A faulty oxygen sensor could also cause that, but injectors are a common culprit. Sometimes it's just a clogged EGR valve messing with the air/fuel mixture too.

Interesting. When your injectors were failing, were you also getting jerking during acceleration?

Yep, the jerking was definitely there, especially under load. The check engine light was intermittent at first, then stayed on solid. If you suspect fuel injectors, get them checked. Could save your catalytic converter in the long run. If you don't have the tools to diagnose, it's probably best to get it to a workshop. They'll be able to run proper diagnostics.

Turns out the injector on cylinder 3 was defective. Replacing all four injectors cost me 515€. It runs like new now. Thanks for the input.