Air Flow Meter

1982 Porsche 928 Automatic TransSECTION Air Flow Meter

All engine air is drawn through the air flow meter. The meter contains a tunnel with measuring flap and dampening flap (offset 90° on same casting). The measuring flap swings in air stream against pressure of a spiral spring and is connected to a potentiometer.

The potentiometer transmits an electrical signal determined by the measuring flap position to inform the ECU of engine load. See Fig 1. In addition to monitoring the air flow, the meter also controls fuel pump operation and idling. At idle, the measuring flap is almost closed due to spiral spring pressure.

An idle air by-pass receives air from main air flow through a small hole, the size of which is controlled by the idle mixture screw. This adjustable air by-pass influences CO levels at low engine speeds.

Fig 1: Bosch AFC Air Flow Meter
G09315243Courtesy of BMW OF NORTH AMERICA, INC.
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.