Note. The procedure for adjusting the quality of the idle air-fuel mixture described below can only be taken as a temporary setting. The final installation must be carried out by a specialist dealer department of the vehicle manufacturer using a gas analyzer.
Before proceeding with the adjustment of speed and quality of the idle mixture, make sure that the following conditions are met:
- The air cleaner element is clean and installed;
- The engine is warmed up to normal operating temperature;
- The ignition timing and spark plug gaps are set correctly;
- All onboard electrical consumers are switched off;
- All vacuum hoses are correctly connected and securely fastened to their fittings;
- The fuel level in the carburetor float chamber complies with 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 per minute, then drop it back to idle.
Models 3.0 l
1. Fully screw in the mixture adjustment screw until it rests lightly on the seat. Back out the screw approximately four turns. During the adjustment of the quality of the mixture, the possibility of stopping the engine is not ruled out.
2. Adjust the position of the throttle stop screw until the idle speed is 800±50 rpm.
3. By turning the mixture quality screw, achieve stable engine operation at maximum speed.
Models 4.2 l
1. On models with AT, move the selector lever to the position "D" 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 - screw for adjusting the quality of the idle mixture
3. Turn the throttle stop screw to set the engine idle speed to 650±50 per minute.
4. Fully screw in the mixture adjustment screw until it rests lightly on the seat. Back out the screw approximately four turns. During the adjustment of the quality of the mixture, the possibility of stopping the engine is not ruled out.
5. Adjust the idle speed again by turning the adjusting screw.
6. Turn the mixture quality screw until the engine is stable at maximum speed, then turn the screw one full turn clockwise.
7. Using the speed adjustment screw, again achieve idle engine speed of 650±50 per minute.