I just bought this Q7 4.2 and drove it over 100 miles to get it home, the only code it had when I test drove it was the brake booster mech failure, no other codes on test drive or on the way home. But now 200 miles later it throws all three of these codes after about 5 miles of reseting.... lean on both banks at idle and brake booster failure. brakes are maybe a little stiff but not bad, idle is good and smooth, cant find any vac leaks. thier is some suction when I remove the oil cap but not much, but idle does change slightly.
I don't see many of the 4.2's in my area and no Q7's so not real familiar with them. I plan on ordering the PCV valve but it will take a few days to get one, any thing else I should be looking at?
the A/c condensor drain was plugged and it was dripping water on the carpet on the ride home so I did clean it out when I got the truck home ,but I don't see any vac lines around their I could have knocked loose?? that is all that has changed from the time of the test drive to the next morning. (basically I just used a yard stick to wiggle the drain nipple to get it to drain)