LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Ford >> 1977 >> Bronco Automatic Trans >> Repair and Diagnosis >> Engine Performance >> Fuel Delivery >> DECEL Throttle Modulator >> Adjustment
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DECEL Throttle Modulator: Adjustment

NOTE: This adjustment is to be performed when replacing components found defective during testing sequence.
  1. With engine at normal operating temperature and transmission in Neutral, adjust carburetor to specified curb idle speed. On automatic transmission vehicles, this will be set to 100 RPM higher than specified curb idle speed (as with transmission in Drive), although transmission will remain in Neutral. This is to keep minimum load on engine.
  2. Disconnect vacuum hose from throttle modulator and plug hose. Connect manifold vacuum source to diaphragm. Allow one minute for engine speed to stabilize. If engine speed is within specifications, the modulator is properly set. Go to step  5.
  3. If RPM was not within specification, adjust throttle modulator by loosening lock nut and turning until speed is within limits. Retighten lock nut.
    NOTE: On Carter 1-barrel carburetors, avoid damage to diaphragm by holding diaphragm shaft with 1/4" wrench while turning adjusting screw with 3/8" wrench.
  4. Detach manifold vacuum hose from modulator and allow engine to return to idle condition. Repeat procedure from step  2 as required until proper function occurs.
  5. Disconnect manifold vacuum hose from modulator and allow engine to return to normal idle. Remove plug from original hose and reconnect it to throttle modulator fitting.
  6. On automatic transmission vehicles, reset idle to specifications with transmission in Drive. On all vehicles, stop engine. Install air cleaner assembly.
scientia non olet · About LEMON Manuals