9000 L4-1985cc 20L DOHC (1986) Air Flow Meter/Sensor Locations
Description
The mass air flow sensor, located between the air cleaner and intake manifold, measures the air mass passing through it. In air mass measurement (and
not air volume measurement), the changes in air density which occur with every change in air temperature and air pressure are taken into account.
Since the mass air flow sensor measures the mass of the air and not just the flow, it is important to ensure that no air leakage occurs after it on the
downstream side.
The most important parts of the mass air flow sensor are a thin filament (hot wire) of platinum and a temperature-dependent resistor. The temperature
of the filament is maintained at a constant 1 00°C (212°F) above the temperature of the inlet air (aluminium mass air flow sensors). In mass air flow
sensors of plastic the temperature difference is 120°C.
In the LH 2.4.1 and 2.4.2 systems the temperature difference is increased to 155°C (310°F) for higher measurement accuracy.
Control of the current needed to maintain the filament at a constant temperature is effected by a bridge circuit and a detector resistor. The voltage
variations are directly proportional to the mass of the inlet air.
The electrical components are grouped in a module on the mass air flow sensor casing. This module also contains a potentiometer for adjusting the CO
content at idling speed (only LH 2.2 and LH 2.4.2 on cars without a catalytic converter).
Note: The components shown in the illustration are not available as spare parts.
