Dynamic testing of MAF

[erubin]

2000 430clk.
Got CEL P0170 and P0173. Likely suspect is the MAF. MB provided the following test. Place car in 3rd gear. Accelerate at WOT and record the MAF when engine hits 4000 RPM. For this car the MAF should show somewhere around 525kg/hr (from memory, don't remember exact figure). I measured 400kg/hr. car lacks power at WOT. Will replace the MAF because it failed the test. Idle is perfect (smooth) so vacuum leak is unlikely.

Before deciding to replace the MAF always try disconnecting and reconnecting the MAf (with engine off). Sometimes the contacts develop an oxidation layer that falses the readings. Reconnecting can "clean" the contacts. In my case it made no difference and I still read about 400kg/hr.