Here's a good sanity check for the status of your MAF. Do a full-throttle run all the way to
redline in a single gear (second works fine). Group 002 shows air mass in g/s. Your peak
airflow should be roughly 0.80 times your horsepower. So, if you have a stock 150hp 1.8T,
expect around 120g/s. If you have a 225hp 1.8T remapped to 265hp, expect around 200g/s.
If you see significantly less than that, you MAF may be on the way out. This also works if you
are chipped, but "race" programs may make more power through timing, rather than airflow.
Therefore, take all readings with a grain of salt. Also remember that the MAF can be
knackered even if all values look reasonable!
0.8x 210 = 168g/s
If you suspect your MAF is bad, one way to test it
is to unplug the MAF, often if the MAF is giving false readings and upsets the fueling. If you
unplug it, the ECU will ignore the MAF and run off of baseline tables. Be careful, as a boost
leak or a vacuum leak can be miss-diagnosed as a bad MAF, because they will throw off the
readings on the MAF. (Air sneaks around the MAF).
To check for a VAC leak, log block 032
and check the idle fuel trims. If itâs more than +2% you probably have a VAC leak
somewhere. Check hoses and connections for loose clamps of cut hoses here are come
common areas for VAC leaks.
Turbo inlet pipe not secured, DV line leaking, Crank case breather Y pipe split, Line on Fuel
pressure regulator gets worn and leaks, intake manifold gasket can leak, and PCV line under
intake manifold leaks. To find leaks some people spray ether or starter spray around in the engine bay and listen for changes
Boost Leak â View Block 032 with VAG-COM. If Fuel Trims are Negative more than 5% in
the load range there is a very good chance that there is a leak after the turbo. Visual
inspection of clamps, hoses for a loose connection is the best way to look for leaks. A
common place for leaks is at the entrance to the pancake pipe located in the passenger side
fender. Also the small line on the DV can rip. See also section 2.4.
