my vr is getting around 20mpg - as indicated by the mfa. ive recently added a 6 branch and changed a bunch of sensors as it was playing up (eddie if youre reading this is turned out to be the lambda sensor), but since ive done that the economy isnt doing too well. vagcom doesnt give me any fault codes and it doesnt smell like its massively overfuelling either. theres a very slight smell of burning oil and bit of grey smoke on overrun (stem seals?) and thats about it. ive tried looking for vacuum leaks by spraying the intake pipes with carb cleaner but that all seems to be in order. i dont know what else to check, could someone help me out? could the mfa be lying?
town driving. i should be getting at least 30mpg. i know the MFA isnt the most accurate thing but it cant be this far off?!
im pretty sure you can because thats what the MFA said. regardless of whether you can or you cant - the MFA now says around 20mpg whereas it was 30mpg before. need help guys, not arguing over whether its possible or not.
correction - it does smell like its running rich. defo overfuelling, but what would cause this? the blue coolant temp sensor has been changed along with the cam sensor and the lambda sensor and there are no fault codes appearing now.
First thing i would do is work out what your MPG actually is using an ancient Greek method called Mathmatics. Its fairly accurate from what I understand. Number of miles divided by number of gallons put in your car. Do that and your'll be able to figure out if your car has crap Fuel ecomony or the MFA is lying. Mine constantlty reads about 5 mpg over its true value, but I have seen them under read by alot as well.
as above i always reset the trip miles ever time i fill up its the only way to tell if you are using more fuel or not
Yes, but if your MFA is code-F, then the `drop` might be because of that rather than a drastic rise in consumption... What you need to do is this; Brim the tank, then drive a decent distance (say, 50 miles or so), then brim the tank again, taking note of how many litres it takes. Divide the number of litres by 4.5 to convert to gallons, then divide 50 (or however many miles you did), by this figure to get your actual MPG. If that comes out as a decent figure; case solved. One goosed MFA. If not then you can start looking at the whys and where-fors.
its pretty obvious its running rich, i dont think i'll be needing to do any tests to confirm it. where do i go from here? could a slight exhaust leak before the lambda sensor be causing this?
As said, you need to work out your true mpg MFA is full of poopie at the best of times until you do that, you may be looking for a problem that isn't there. How does it smell like its running rich? Whip the spark plugs out then take a picture and post here and someone will tell you if its running rich. 20mpg from a VR in town isn't too bad anyway I'd have said....
well if im doing 40 in 5th i should be getting around about 30mpg right? it was showing around 20. im pretty sure ive sussed the problem now. i scanned the car and the maf sensor decided to throw a code, so i cleared it and went on a drive. mpg picked up to what it should be so ive ordered a new maf. anyway thanks for your help guys.
