1971 and some later models are equipped with a Combination Emission Control (CEC) solenoid. This solenoid does not function as an idle speed solenoid, and should not be adjusted during a routing carburetor adjustment.
- Set the parking brake and block the drive wheels.
- Start the engine and run it to normal operating temperature. Make sure that the choke is fully open before you make any adjustments.
- You can set the idle solenoid with the air cleaner removed, but Oldsmobile states that the air cleaner must be in place to set the idle mixture.
- Disconnect the fuel tank hose from the vapor canister, and disconnect the EGR valve hose.
- Disconnect the distributor vacuum hoses from the CEC solenoid and plug the hose leading to the carburetor.
- Make sure the air conditioner is turned off if the car has one, and that the dwell and timing are correct. If the car has an automatic transmission, it should be in Drive. Manual transmission cars should be in neutral.
- Connect a tachometer to the engine if you haven't already.
- On 1971 models, set the correct idle speed by turning the idle speed adjusting screw. Since this carburetor has a CEC solenoid instead of a throttle solenoid, no other adjustment is possible. The idle mixture is set the same as later model carburetors.
- On later model carburetors (75-76), turn the throttle stop solenoid inward or outward to obtain the higher of the two idle speeds listed in the tune-up chart.
- Disconnect the solenoid wire and insert a 1 / 8 in. Allen wrench into the end of the solenoid to obtain the lower of the two listed idle speeds. If the car is equipped with an automatic transmission, this adjustment should be made with the transmission in Park.
- To set the idle mixture, increase the idle speed to about 1,000 rpm over the specified setting and then cut the tab off the limiter cap. Turn the mixture screw counterclockwise until the maximum possible rpm is reached. Then reset the idle speed to 100 rpm over the specified rpm (with the idle speed screw, not the mixture screw).
- Turn the idle mixture screw clockwise until the idle speed reaches the specified setting.
Idle mixture is set at the factory, which is why the mixture screws are capped. If you richen the mixture, you alter the emission levels. Normally, idle mixture does not need adjusting. If, however, you adjust your idle mixture, you should take your car to a dealership or a garage where the emission level can be checked with a CO meter.