Air flow meter
Discussion
Testing is performed in the following manner. Peel back the rubber boot on the airflow meter connector and leave it plugged in to the airflow meter. Set up the digital multimeter to read voltage. Insert the negative probe into the Red/Black wire (sensor ground), and the positive into the Blue/Green wire (Airflow signal).
Turn on the ignition, but do not start the engine. The meter should immediately indicate a reading of approximately 0.3-0.34 Volts after the initial "warm up" spike. Most defective airflow meters will overshoot to 0.8 Volts or higher, and take at least 2 seconds to come down to the correct voltage.
Now start the engine, and the reading should rise to 1.6 Volts (3.5 Litre engine) to 1.75 Volts (5.0 Litre engine).
The next test is full load, and as with the fuel pressure test it will require use of a rolling road or a steep hill in the same manner. Under full load the voltage should rise to 4.45 Volts (3.5 Litre engine) to 4.95 Volts (5.0 Litre engine).
Turn on the ignition, but do not start the engine. The meter should immediately indicate a reading of approximately 0.3-0.34 Volts after the initial "warm up" spike. Most defective airflow meters will overshoot to 0.8 Volts or higher, and take at least 2 seconds to come down to the correct voltage.
Now start the engine, and the reading should rise to 1.6 Volts (3.5 Litre engine) to 1.75 Volts (5.0 Litre engine).
The next test is full load, and as with the fuel pressure test it will require use of a rolling road or a steep hill in the same manner. Under full load the voltage should rise to 4.45 Volts (3.5 Litre engine) to 4.95 Volts (5.0 Litre engine).
thanks again The problem you have is chicken and egg. If the engines running rough the AFM will reflect this, as the air being drawn is is likley to be unstable. You are best reading the voltages with moving coil meter to smooth the avarage reading out, a DVM will be pretty useless. As long as the idle is within about 100 mv of the correct readings it should be OK. Again the problem is what the idle is at, + /- 100 RPM makes a big difference to the reading.
Heres the start trace, with an idle voltage of 1.6 volts (3.9) .
If this is correct the AFM is likely to be basically OK.
Im around for the next week or so on leave if you do want to drop over (Saturdays booked up) . I now have the Steve heath ECUMate, but no faulty cars so feel free.
Heres the start trace, with an idle voltage of 1.6 volts (3.9) .
If this is correct the AFM is likely to be basically OK.
Im around for the next week or so on leave if you do want to drop over (Saturdays booked up) . I now have the Steve heath ECUMate, but no faulty cars so feel free.
Edited by blitzracing on Sunday 8th April 09:24
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