1978 BMW 633CSi Automatic TransFACTORY OEM SERVICE PROCEDURE

EGR Valve: 320i

  1. With engine idling at normal operating temperature, disconnect Blue vacuum hose from EGR valve. DO NOT plug hose or connection. Engine speed should not change. If speed drops, either EGR valve is defective, throttle idle setting is out of adjustment, or Red vacuum hose from thermo valve is leaking or plugged.
  2. With Blue hose still disconnected, pull Red hose from EGR valve. Disconnect Black hose from intake manifold and connect it to Red hose connection on EGR valve. Engine speed should now drop considerably. If speed does not drop, EGR valve is defective.
  3. With Red hose disconnected from EGR valve and Black hose connected to EGR valve, reconnect Blue hose to EGR valve. Engine speed should not change. If speed drops, vacuum hoses are leaking or plugged, EGR valve is defective, or pressure transmitter is defective.
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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.

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