Black exhaust tip

I'm getting a soot staining on my stainless exhaust tip after a very few miles after cleaning and polishing it. Is this normal? How long does it take for your exhaust tips to discolour, or get soot all over them?

 

Probably not normal after a few miles. Might be time to check the fueling setup?

 

i never clean my zorst.. looks quicker if it's stained!

 

Mixtures too rich probably - just keep using the autosol on it!

 

I take it a custom remap is the only way to sort a rich mixture on a fuel injected car?

 

if it rich in general, the whole thing can be leaned out. How i dont know, i know how to do it on the G60, you adjust the CO pot on the MAF.

 

I bet there is something similar. Mabe a sensor isn't working correctly giving incorrect values to the ECU. A job for VAG COM I'd say.

 

k, it's going in for a service in a week, they'll be plugging it in to the "matrix" then i think. it should come up if something is wrong with a sensor shouldnt it?

 

I may be wrong but the water temp sender could be dodgy. I had this trouble on my last 8v, the ECU always thought it was cold, hence it over fuelled aand i got exhaust blackening.

 

I have noticed that it's a bit worse on MPG recently. Even on long mway runs its going through more petrol than it used to. I had got over 300miles from a tank of optimax, now it wont get to 280.

 

It could be the lambda sensor playing up! Has it still got the cat on?

 

yup, still got the cat on.

So should I specify for VW to check:

the lambda sensor
water temp sendor

anything else I can do myself, can I check these myself?