maf readings

have a td4 here and when the maf output is measured on the multimeter,voltage, it appears to read correctly. 2.1v tickover rising on acceleration. when the airflow data is monitored on a delphi 150 diagnostic system the reported airflow rate doesnt folow what the meter is showing it staggers behind a lot. voltage measurement taken at ecu pins to rule out any wiring errors. now im going by some data from tunning diesels and i was wondering if anyone had the data that relates voltage to airflow reading. i am starting to suspect an internal error with the ecu as the previous sensor showed reduced airflow on first acceleration on the delphi and was changed. i am waiting for a genuine maf sensor but as i say the voltage readings read ok.

You can't really measure the voltage output of an airflow meter accurately with a multi-meter. What you really need is an oscilloscope to check for any excess noise or voltage spikes, and to graph the output to get a better picture. Chances are your multi-meter is just not fast enough to be picking up what the ECU is seeing.

From your description it could be the diagnostic system is just registering the live data slowly, perhaps not a very good PID refresh rate, hence why it is 'staggering' behind.

Best bet is to disconnect the MAF sensor, see if the vehicle improves - if it does fit a genuine MAF or a Bosch sensor and be done with it.

i feel dumb. realized on the delphi system it measures maf in mg/injection. figures i had to go by were measured in something like kg/minute. basically the maf reading i was seeing wouldnt change much till the turbo kicked in. borrowed the system and not used to it. multimeter was keeping up with voltage change i was stumped as to why maf reading didnt climb. if i had read the measurement scale more carefully i would have realized. finding test information on bosh sensors is not easy. pierburg is easier. autodata give 3 voltage measurements so will try again in the morning. basically the sensor in is the wrong one. its close but i dont know how close.