I own an 2012 Scirocco 2.0 TSI (same engine as MK6 GTI I think) and I am having a hard time fixing this problem.
The issue is that the check engine light turns on with a P0172 code (system to rich) and the car has all kinds of symptoms:
-hesitation on throttle
-unburnt gas smell
This is the weird part, these symptoms only occur in warm weather, so if the car is in the hot sun all day it runs badly but if its cold for a few days the problem goes away and the light turns off.
So the car is fine in the winter but has problems all summer. Also in the summer sometimes the problem disappears after long road trips.
So far I have gone to 2 different shops as well as the VW dealer and did not have any success; here is what I replaced so far:
-purge valve solenoid
-throttle body cleaned and reset (done by VW dealer)
I have owned this car since new and it is fairly low mileage (95.000km) , the only things replaced before were the timing chain and the clutch.
Any help is appreciated!