Table of contents: 3.0L models ↓ Models 4.2L ↓
Note: The procedure for adjusting the idle air-fuel mixture quality described below should be considered only as a temporary setting. The final setting should be performed by a specialist at the dealership of the vehicle manufacturer using a gas analyzer.
Before you begin adjusting the idle speed and mixture quality, make sure that the following conditions are met:
- The air cleaner filter element is not dirty and is installed;
- The engine has warmed up to normal operating temperature;
- The ignition timing and spark plug gaps are set correctly;
- All on-board power consumers are switched off;
- All vacuum hoses are properly connected and securely fastened to their fittings;
- The fuel level in the carburetor float chamber meets regulatory requirements;
- The air damper is fully open.
1. Connect a reliable tachometer to the engine. Start the engine and warm it up to normal operating temperature.
2. Raise the engine speed several times to 2,000÷3,000 rpm, then lower it back to idle.
3.0L models
1. Turn the mixture quality adjustment screw all the way in until it lightly touches the seat. Turn the screw back approximately four turns. The engine may stall while adjusting the mixture quality.
2. Adjust the position of the throttle stop screw to achieve an idle speed of 800±50 rpm.
3. Turn the mixture quality screw until the engine runs stably at maximum speed.
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Models 4.2L
1. On models with automatic transmission, move the selector lever to the "D" position and firmly apply the parking brake.
2. The location of the adjusting screws on the 4.2L engine carburetor is shown in the accompanying illustration.
1 - idle speed adjustment screw
2 — idle mixture quality adjustment screw
3. By turning the throttle stop screw, set the engine idle speed to 650±50 rpm.
4. Turn the mixture quality adjustment screw all the way in until it lightly touches the seat. Turn the screw back approximately four turns. The engine may stall while adjusting the mixture quality.
5. Adjust the idle speed again by turning the adjusting screw.
6. Turn the mixture quality screw until the engine runs stably at maximum speed, then turn the screw one full turn clockwise.
7. Using the speed adjustment screw, again achieve an idle engine speed of 650±50 rpm.