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Home >> Mercedes Benz >> 1975 >> 280 >> Repair and Diagnosis (Single Page) >> Engine Performance >> Engine Control Systems >> Exhaust Emissions System - Exhaust Gas RECIRCULATION >> Testing >> Vacuum Control/Throttle Lift >> 1974 230 Models
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1974 230 Models

  1. Connect tachometer to engine. Start engine and slowly increase speed to 2500 RPM. Release accelerator and observe vacuum governor on carburetor.
  2. Above 2000 RPM, adjustment screw should contact operating lever on carburetor. Below 1800 RPM, diaphragm should be retracted and adjustment screw should not touch lever.
  3. If throttle valve lift does not work as indicated, check vacuum hoses for damage and proper routing. Also check RPM switch and EGR switchover valve.
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