Hi..

What's the oil separator for? What does it do and could it cause my Fabia to lose power under load even though it starts easily?

No codes showing, even with a VAGCOM.

Its job is to separate crankcase oil/oil mist from the air being scavenged through the crankcase, it does that by having a cyclonic separator built into it - that causes the oil to drop out of the air, or at least quite a lot of it to drop out, and drop down into the sump instead of getting into the combustion chamber and burning along with the fuel in the cylinders. One thing that it does is effectively cause the fuel mixture to lean back and also to now have a mix of petrol and oil, which has too low an octane rating - and that will cause pinging/pinking - been there and needed to replace the oil separator though I didn't exactly work out what had gone wrong, though possibly the innards were now coked/coated and so not dropping out the oil as well as originally.

Edit:- are you hearing pinging/pinking under load, especially at lowish revs?

Edited 7 October, 20257 Oct by rum4mo

Thanks..

My 2006 Fabia 1.4 16v, starts easily, idles smoothly and revs fine but under load goes into limp with a max 10mph. No pinking sounds..

No codes showing on a VAGCOM, but I have reset the ECU, replaced and affirmed the TB, new plugs, fuel filter, air filter, oil and filter, new ATF, new coilpacks, checked on all the pipework as well as various sensors. Compression is good too.

Next is the crank and cam sensors, the separator, the fuel injection relay, and maybe the fuel pump.

If it's not running again after that, I don't know what I'll do, as its only got 90k miles on it, no rust and in great condition throughout. Its been a delightful car to drive these past 6 years and I really want it sorted, but so far, despite scanning and much head scratching, it's still just limping along. Just wish I could see a code! 🙁