My car is a 2004 VW Golf Mk5 (1.4 Fsi, european), petrol, 130 000 km, and I just bought it 2 weeks ago from a dealer. A few days ago I started to notice that when I start up with 1st shift on (and i think Reverse as well), the engine works at ~1000 rpm. When I start the engine at Neutral, it works at ~650 rpm, and i feel the engine shaking and making something like a knock sound on the back of the engine. When stopping at red lights, with 1st gear and clutch depressed, it also goes back to 650 rpm and I feeling the same shaking. I would love some help here, because I want to have some ideas of what may be causing this, before taking it to the dealer just to hear a "ok, this is a completely normal situation". Thank you very much for your help.
My car has a manual transmission.
Hello there, a few possible items can cause a similar noise to what you describe. Most likely it is an engine misfire, fuel pump problem, worn out fuel filter, dirty idle air valve (which you may be able to clean), or an oxygen sensor. I’d start by examining these components and trying the tips outlined in the linked articles. If you still need help, a qualified technician such as one from YourMechanic will be able to diagnose this fault and perform any repairs required.
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