Idle Mixture Adjustment
Fig. 1 Propane enrichment specifications. 1983-85 V6-173 w/ 2SE carburetor:
V6-173 Engine W/2SE Carburetor
Idle mixture adjustment requires artificial propane enrichment. Propane enrichment tool J-26911 or equivalent, is required to adjust idle mixture. Air cleaner must remain in place during adjustments. A/C control, if equipped, must be in off position.
1. Set parking brake, then block drive wheels.
2. Disconnect and plug vacuum hoses as directed on vehicle emission label.
3. Check and, if necessary, adjust ignition timing.
4. Connect tachometer to engine following manufacturer's instructions, then start engine and allow to reach normal operating temperature.
5. Set curb idle speed to specifications.
6. Disconnect crankcase ventilation tube from air cleaner. Insert hose with rubber stopper from propane valve into opening in air cleaner. Propane cylinder must remain upright during adjustments, and cylinder must be adequately filled to ensure correct propane flow.
7. With engine idling in Drive (auto. transmission) or Neutral (man. transmission), slowly open propane valve while observing tachometer. Continue to open valve until RPM begins to drop, and note maximum enriched idle RPM.
8. If maximum enriched idle RPM is within specifications, Fig. 1, proceed to Step 15.
9. If enriched RPM is not within specification, remove mixture screw concealment plug as outlined under ``Concealment Plug Removal'' in the appropriate carburetor section.
10. Turn mixture screw inward (clockwise) until lightly seated, then back out until engine just runs (approximately 3 turns).
11. Start engine, then place transmission in Drive (manual transmission in Neutral).
12. Back out mixture screw 1/8 turn at a time until maximum idle speed is obtained, then set idle speed to maximum enriched idle RPM. Maximum idle speed is idle RPM plus propane enrichment RPM.
13. Turn mixture screw inward (clockwise) until specified curb idle speed is obtained, then recheck maximum enriched RPM. If not within specifications, repeat steps above.
14. Check and, if necessary, adjust fast idle speed.
15. Turn ignition off, remove propane tool, then reconnect crankcase ventilation and vacuum hoses.
V6-173 Engine W/E2SE Carburetor
The E2SE carburetor is used with electronic fuel control systems which control air/fuel mixture during all ranges of engine operation. Because of this system control, special preliminary checks and adjustment procedures are required. Procedures must be followed exactly, in sequence, to insure correct mixture adjustment.
The dwell reading from the Mixture Control (MC) solenoid is used as an adjustment calibration. While it is normal for dwell readings to fluctuate over a 5° range, temporary mixture variations may cause dwell reading to fluctuate as much as 10°-15°. Dwell readings specified for adjustment are the average of the most consistent variation.
Fig. 2 Carburetor mixture control adjustment. V6-173 w/E2SE carburetor:
PRE-SET PROCEDURE
1. Remove plug covering idle mixture adjusting screw as outlined under ``Concealment Plug Removal'' in the appropriate carburetor section. Turn mixture screw in (clockwise) until lightly seated, then back screw out 4 turns.
2. If plug covering idle air bleed valve , Fig. 2, has been removed, inspect valve for blockage and replace plug or air horn. If plug is in place, do not remove plug.
3. Remove vent stack screen to gain access to lean-mixture screw in bottom of float bowl, Fig. 2.
4. Turn lean mixture screw in (clockwise) until lightly seated, then back screw out 2-1/2 turns.
5. Install carburetor on engine with air cleaner off and related vacuum fittings plugged.
6. Disconnect bowl vent hose at carburetor. Disconnect and plug vacuum hoses at EGR valve and ``T'' fitting in bowl vent hose. Disconnect canister purge hose at carburetor and plug vacuum fitting.
7. Remove secondary vacuum break thermal vacuum switch from air cleaner, then disconnect hose to thermostatic air cleaner from switch and plug fitting on switch. Leave all other vacuum hoses connected to switch.
8. Connect dwell meter to test lead (green wire) in MC solenoid harness and set meter on 6 Cylinder scale. Connect tachometer to engine following manufacturer's instructions.
9. Start engine and run at fast idle until engine enters ``Closed Loop'' mode of operation, indicated by a fluctuating dwell reading. On 1985 units, push TPS plunger downward and insert a 1/8 inch spacer between plunger and lever.
MIXTURE ADJUSTMENT PROCEDURE
Perform adjustments with automatic transmission in park, manual transmission in neutral, unless otherwise noted.
1. Run engine at 3,000 RPM and adjust lean mixture screw, as needed to obtain a dwell reading of 35°. If reading is too low, turn screw counter-clockwise; if reading is too high, turn screw clockwise. Make adjustments in small increments, allowing time between adjustments for engine and dwell meter to stabilize.
2. Return engine to idle.
3. Adjust idle mixture screw, as needed, to obtain a dwell reading of 25°. If reading is too low, turn screw counter-clockwise; if reading is too high, turn screw clockwise. Make adjustments in small increments, allowing time between adjustments for engine and dwell meter to stabilize. Make final check with mixture adjusting tool removed.
4. Disconnect wiring harness connector to MC solenoid. Engine speed should change at least 50 RPM. If not, check for restriction, leak, etc. in idle air bleed circuit.
5. Run engine at 3,000 RPM while observing dwell meter. Meter should indicate fluctuating dwell with an average reading of 35°. If reading is not within specifications, repeat steps 1-5.
6. Reinstall vent screen stack, remove TPS spacer (if applicable), reconnect vacuum hoses to proper fittings, and reinstall air cleaner. Check and, if necessary, adjust curb idle speed to specification.