Throttle Valve

The factory-set throttle valve adjusting screw is not used to set idle speed. Its only function is to provide a mechanical stop for the linkage to prevent damage to the throttle plate and housing. It should be adjusted only if the factory setting has been changed.

Throttle Valve Vacuum Hoses Digifant II:

1. To check the adjustment, disconnect the vacuum line that comes from the carbon canister control valve and connects to the throttle body. Connect a vacuum gauge in its place. At idle there should be approximately zero vacuum. Up to 1 in. of vacuum is acceptable. If the vacuum gauge measures greater than 1 in. of vacuum at idle, the throttle valve basic adjustment should be corrected.

2. Check the vacuum hose fittings at the throttle valve for proper vacuum signal as some fittings can become plugged, this is due to the introduction of PCV vapors near the throttle valve. If signs of PCV residue are found, remove the intake air hose and visually check the throttle valve. Clean the vacuum fittings and throttle valve with spray type carb-cleaner as needed.

Throttle Valve Adjusting Screw:

3. To correct a faulty throttle valve adjustment, loosen the locknut and back off the throttle valve adjusting screw until there is clearence between its tip and the throttle lever. Place a thin piece of paper between the screw and the lever and turn the adjusting screw in. When the screw is just barely gripping the paper, remove the paper and turn the screw in an additional 1/2 turn. Tighten the locknut.