Air/Fuel Mixture: Adjustments

Prior to performing the idle mixture adjustment, the idle mixture screw concealment plugs must be removed. Refer to ``Concealment Plug Removal'' procedures in the ``Carburetor Section''.

Fig. 5 Dwell & tachometer connections for idle adjustments. 1983 4-151/2.5L California engines:

1983 4-151/2.5L ENGINES

California Models W/ Rochester E2SE 2 Barrel Carburetor

1. Remove air cleaner, then disconnect bowl vent hose from carburetor.
2. Disconnect EGR and canister purge vacuum hoses at carburetor and cap carburetor ports.
3. Connect a suitable tachometer between distributor Tach terminal and ground.
4. Connect a suitable dwell meter Mixture Control Solenoid (MCS) test lead, Fig. 5.
5. Position transmission selector lever in Neutral with parking brake applied and drive wheels blocked.
6. Start engine and allow to operate at fast idle speed for atleast 3 minutes.
7. Return engine to idle speed and reset idle speed to 700 RPM.
8. Adjust idle mixture screw to obtain an average dwell of 25°, using tool No J-28706 or a 3/16 inch thin wall deep socket. If dwell is too low, back out adjusting screw. If dwell is to high turn in adjusting screw. When adjusting, allow time dwell to stabilize. If proper dwell reading can not be obtained, check idle system for leaks, restrictions etc.
9. Disconnect MCS connector and check for an idle speed change of atleast 50 RPM. If idle speed does not change by atleast 50 RPM, check idle air bleed circuit for restrictions, leaks etc. Reconnect MCS connector.
10. After making necessary adjustments, reset curb idle speed to correct setting, then reconnect EGR, canister purge and bowl vent hoses.




Federal Models W/ 2SE 2 Barrel Carburetor

1. Turn idle mixture screw clockwise until lightly seated, then back screw three turns.
2. Connect a suitable tachometer to engine, then start engine and allow to reach operating temperature.
3. Check to ensure idle speed is set to the correct RPM.
4. Turn idle mixture screw in the clockwise direction until a loss in RPM is noted.
5. Turn idle mixture screw in the counterclockwise direction until the maximum RPM is obtained. Do not turn idle mixture screw beyond the point at which the maximum RPM was obtained.
6. Turn idle mixture adjusting screw in the clockwise direction until the specified lean drop 100 RPM is obtained.
7. If idle speed differs more than 30 RPM for the correct idle speed setting, reset idle speed and perform steps through 6.
8. Set idle speed to specifications and reinstall air cleaner.