Idle Mixture Adjustment Cadillac Brougham I

1. Using Remover/Installer (J-29030-B or BT-7610-B), remove both idle mixture screws and springs. Inspect needles for damage and needle openings for damage or foreign material.
2. Reinstall mixture screws and springs in throttle body. Using remover/installer, turn both mixture screws clockwise until lightly seated. Turn each mixture screw counterclockwise 3 turns.
3. Reinstall carburetor on engine using a new flange gasket. Proceed to IDLE MIXTURE CONTROL ADJUSTMENT step 9) to finalize correct dwell reading.

Scheme 8

1. Mixture control solenoid must be checked before adjustment. Stop engine. Remove air cleaner and gasket. Insert Float Gauge (J-34935-1 or BT-8420-A) in "D" shaped hole in air horn (next to idle air bleed valve cover). Gauge checks float level externally. It may be necessary to grind material off gauge to allow it to enter hole.
2. With gauge installed, read and record gauge mark that lines up with top of air horn. Lightly press down to bottom gauge. Total travel should be 1/16-3/16" (1.6-4.8 mm). If travel is correct, go to step 3). If float travel is not correct, carburetor must be disassembled and readjusted.
3. Set parking brake and block drive wheels. Disconnect and plug canister purge hose. Connect tachometer to engine. Check ignition timing and adjust, if necessary.
4. Connect a dwell meter to Green wire from mixture control solenoid in carburetor. Set dwell meter on 6-cylinder scale. Warm engine to normal operating temperature. A varying dwell should be noted on dwell meter. NOTE: Engine must be run to ensure coolant temperature sensor and oxygen sensor are at full operational temperature.
5. Adjust curb idle speed (on models with ISC or ILC, do not adjust). With engine idling in Drive (Neutral on man. trans.), observe dwell reading. If dwell needle is moving within a range of 10-50 degrees, no adjustment is necessary. If needle is fixed at one point or outside of this range, see SYSTEM PERFORMANCE CHART in the appropriate TESTS/CODES article in the COMPUTER ENGINE CONTROL section. If adjustments are necessary, proceed to next step.
6. Stop engine. Cover carburetor air intakes and vents with tape. Drill rivet heads on idle air bleed plug (above primary bores). Remove plug and blow out metal chips and rivet pieces.
7. Install Gauge (J-33815-2 or BT-8253-B) in "D" shaped hole on throttle side of air horn. Position gauge so upper end is over open cavity next to idle air bleed valve. (Scheme 8)
8. Lightly hold gauge down to seat solenoid plunger against its stop. Adjust idle air bleed valve so that gauge will pivot over and just touch top of valve. Remove gauge.
9. Start engine and allow it to reach normal operating temperature. Ensure canister purge hose is disconnected and plugged. While idling in Drive (Neutral on man. trans.), adjust idle air bleed valve with screwdriver until dwell varies within 25-35 degree range. Try to get as close to 30 degrees as possible. NOTE: Perform this step carefully. Idle air bleed valve is very sensitive in controlling air/fuel ratios. Valve should be turned only in 1/8 turn increments.
10. If dwell reading does not vary and is not within 25-35 degree range after this adjustment, it will be necessary to remove plugs covering idle mixture screws. After removing plugs, adjust idle mixture as follows.
11. Turn mixture screws in until lightly seated. Back each screw out 3 turns. Install carburetor with new flange gasket. Repeat step 9).
12. If unable to set dwell to 25-35 degrees, and dwell is below 25 degrees, turn both mixture screws out one turn. If above 35 degrees, turn both mixture screws in one turn.
13. Readjust idle air bleed valve to obtain dwell limits. Seal idle mixture screws with silicone sealer or RTV. Mixture control adjustment is complete if dwell at 3000 RPM varies between 10-50 degrees with at least a 300 RPM drop from full rich to full lean.
14. Idle mixture adjustment is complete if closed loop dwell at idle varies between 10-50 degrees with no rough engine idle.