Idle Speed and Mixture
For the idle speed and mixture adjustments, refer to General Information & Maintenance of this repair guide.Accelerator Cable Play
See Figure 1
- With the engine cold, measure and note the amount of deflection of the accelerator cable at the carburetor, as shown in the accompanying illustration.
- Start the engine and allow it to reach normal operating temperature.
- Measure and note the cable play again once the engine is completely warmed up.
If the cable play was not within either of the specified ranges, adjust the cable play as follows:
- Loosen the adjusting locknut.
- Turn the adjusting nut until the cable play is within the specified range.
- Tighten the adjusting locknut securely.
- Allow the engine to cool down, then perform the test procedure again to double check the adjustment.
See Figures 2 and 3
- Inspect the float level by looking through the level inspection window in the side of the carburetor. The float level should fall within the round mark at the center of the level window.
- If the float level is not within the round mark in the window, proceed with the adjustment. Otherwise, the float level is correct.
- Remove the upper air horn from the carburetor and turn it upside-down. Be sure to remove the air horn gasket prior to measuring the float level.
Measure the float level with the all of the float weight applied to the needle valve.
- Using a drill bit or bolt of the proper diameter, measure the distance between the float and the gasket surface of the air horn. The distance should be 0.31 in. (8mm). If the float level is not as specified, adjust it by bending the tongue up or down.
- Install the air horn on the carburetor.
See Figure 4
- Start the engine, and allow it to reach normal operating temperature.
- Ensure that the idle speed is correct; refer to General Information & Maintenance for the proper procedure.
- While turning the tail lights, license plate lights and side marker lights ON, ensure that the idle-up actuator rod moves down (indicating that the idle-up is working).
- Ensure that the heater fan, rear defogger, and air conditioner (if equipped) are all turned OFF. Turn the headlights ON, then check the engine idle-up speed (rpm). The idle-up speed should be 900-700 rpm. If the idle-up speed is not as specified, adjust it by turning the adjusting screw.
- Turn the headlights and other lights OFF.
- Turn the rear defogger ON, and ensure that the idle-up actuator rod moves down, as in Step 3. Perform this step also with the air conditioner and the heater fan. In all three cases, the idle-up actuator rod should move down and increase the vehicle's idle speed to 900-700 rpm.
- If the actuator rod does not move as indicated, there is a problem with the Three-Way Switching Valve (TWSV), the TWSV circuit, or the actuator itself.
Perform the following adjustment with the air intake case removed from the engine, and the engine should be cold.
- Using your finger, check the choke valve for smooth movement.
- When the ambient temperature is below 77°F (25°C) and the engine is cold, ensure that the choke valve is almost completely closed.
- Ensure that the choke valve-to-carburetor bore clearance is within 0.01-0.023 in. (0.1-0.6mm) when the ambient air temperature is 77°F (25°C), and within 0.2-0.8 in. (1.3-2.8mm) when the air temperature is 8°F (40°C).
- If the choke valve-to-carburetor bore clearance is not within the specified ranges, inspect the choke spring, choke piston and each actuating link in the choke system for smooth operation. Lubricate the choke valve shaft and each actuating link with spray lubricant, if necessary.
- If the choke valve-to-carburetor bore clearance is still not within the specified ranges, remove the carburetor from the intake manifold, then remove the idle-up actuator from the carburetor.
- Turrn the fast idle cam counterclockwise and insert a metal pin into the cam and bracket holes to secure it in place.
- Bend the choke lever up or down with a pair of pliers. Bending the lever up closes the choke valve, and bending the lever don opens the choke valve.
- Install the idle-up actuator, the carburetor and the air intake case.
- Start the engine and allow it to reach normal operating temperature.
- Stop the engine once it is warmed up, remove the air intake case, and ensure that the choke valve is fully open.
- If the choke valve does not open fully, the wax element or the link system is defective.
Fast Idle Speed
See Figures 5 and 6
Fast idle inspection and adjustment should be performed when the ambient air temperature is between 71-82°F (22-28°C), and only if the idle-up system is functioning normally.
- Park the vehicle in a garage where the ambient air temperature is 71-82°F (22-28°C) for at least four hours.
- Remove the carburetor and allow it rest for one hour in the same place as the vehicle (the temperature must be 71-82°F (22-28°C) for the carburetor).
- After one hour, inspect the cam and cam follower to ensure that the cam mark is positioned as shown.
- Detach the vacuum hose from the Three-Way Switching Valve (TWSV), and connect a hand-held vacuum pump to the idle-up actuator.
- Apply 15.7 in. Hg (40cm Hg) of vacuum to the idle-up actuator, then measure the clearance between the actuator rod and the idle-up adjusting screw. The clearance should be 0.7-0.12 in. (2.5-3.0mm).
- If the clearance was not within the specified range, adjust it by turning the fast idle adjusting screw.
See Figure 7
This procedure should be performed when the engine is cold.
- Remove the air intake case.
- Ensure that the choke valve is completely closed.
- Open the choke valve fully, and check that the choke valve-to-carburetor bore clearance is 0.7-0.12 in. (2.5-3.0mm).
- If the clearance was not within the specified range, adjust it by bending the unloader arm until the proper clearance is achieved.
REMOVAL & INSTALLATION
- Disconnect the negative battery cable.
- Drain the engine coolant.
- Remove the air intake case from the carburetor.
- Detach and label all of the wiring connectors from the micro-switches, switch vent solenoid valve, fuel cut-off solenoid valve and mixture control solenoid valve.
- Detach the wiring connector from the Vacuum Switching Valve (VSV).
- Remove the EGR modulator and Three-Way Switching Valve (TWSV) from the carburetor.
- Detach the engine coolant hoses from the carburetor.
- Disconnect the accelerator cable from the carburetor.
- Disconnect and label the vacuum hoses from the idle-up actuator and the carburetor.
- Remove the fuel tank filler cap, then reinstall it. This will release fuel tank pressure.
- Detach the fuel inlet hose from the carburetor, and drain any residual fuel from the hose into a small metal catch pan.
- Check around the carburetor for any other wires, hoses or cables which will inhibit carburetor removal.
- Loosen the carburetor-to-intake manifold mounting bolts, then lift the carburetor up and off of the intake manifold.
- Install clean shop rags in the intake manifold hole to prevent accidentally dropping nuts or bolts into the engine.
- Clean the carburetor-to-intake manifold gasket surface thoroughly.
- Along with a new carburetor gasket, install the carburetor on the intake manifold. Be sure to remove the shop rags from the intake manifold inlet hole prior to installing the carburetor.
- Install and tighten the carburetor mounting nuts evenly to 159-248 inch lbs. (18-28 Nm).
- Reattach all vacuum lines, fuel hoses, coolant hoses, and wiring connectors to the carburetor and related components.
- Reconnect the accelerator cable, then adjust it as described earlier in this section.
- Install the EGR modulator and Three-Way Switching Valve (TWSV) to the carburetor.
- Install the air intake case.
- Fill the engine cooling system with the proper amount and type of engine coolant.
See Figures 8 and 9
Efficient carburetion depends greatly on careful cleaning and inspection during overhaul, since dirt, gum, water, or varnish in or on the carburetor parts are often responsible for poor performance.
Overhaul your carburetor in a clean, dust-free area. Carefully disassemble the carburetor, referring often to the exploded views and directions packaged with the rebuilding kit. Keep all similar and look-alike parts segregated during disassembly and cleaning to avoid accidental interchange during assembly. Make a note of all jet sizes.
When the carburetor is disassembled, wash all parts in clean carburetor solvent, with the following exceptions:
Do not leave parts in the solvent any longer than it is necessary to sufficiently loosen the deposits. Excessive cleaning may remove the special finish from the float bowl and choke valve bodies, leaving these parts unfit for service. Rinse all parts in clean solvent and blow them dry with compressed air or allow them to air dry. Wipe clean all cork, plastic, leather, and fiber parts with a clean, lint-free cloth.
Blow out all passages and jets with compressed air and be sure that there are no restrictions or blockages. Never use wire or similar tools to clean jets, fuel passages, or air bleeds. Clean all jets and valve separately to avoid accidental interchange.
Check all parts for wear or damage. If wear or damage is found, replace the defective parts. Especially check the following:
- Check the float needle and seat for wear. If wear is found, replace the complete assembly.
- Check the float hinge pin for wear and the float for dents or distortion. Replace the float if fuel has leaked into it.
- Check the throttle and choke shaft bores for wear or out-of-round condition. Damage or wear to the throttle arm, shaft, or shaft bore will often require replacement of the throttle body. These parts require a close tolerance of fit; wear may allow air leakage, which could affect starting and idling.
Throttle shafts and bushings are not included in overhaul kits. They can be purchased separately.
- Inspect the idle mixture adjusting needles for burrs or grooves. Any such condition requires replacement of the needle, since you will not be able to obtain a satisfactory idle.
- Test the accelerator pump check valves. They should pass air one way, but not the other way. Test for proper seating by blowing and sucking on the valve. Replace the valve check ball and spring as necessary. If the valve is satisfactory, wash the valve parts again to remove breath moisture.
- Check the bowl cover for warped surfaces with a straightedge.
- Closely inspect the accelerator pump plunger for wear and damage, replacing as necessary.
- After the carburetor is assembled, check the choke valve for freedom of operation.
Carburetor overhaul kits are recommended for each overhaul. These kits contain all gaskets and new parts to replace those that deteriorate most rapidly. Failure to replace all parts supplied with the kits (especially gaskets) can result in poor performance later.
Some carburetor manufacturers supply overhaul kits of three basic types: minor repair, major repair, and gasket kits. Basically, they contain the following:
Minor Repair Kits:
Major Repair Kits:
After cleaning and checking all components, reassemble the carburetor, using new parts and referring to the exploded view. When reassembling, make sure that all screws and jets are tight in their seats, but do not overtighten as the tips will be distorted. Tighten all screws gradually, in rotation. Do not tighten needle valves into their seats; uneven jetting will be the result. Always use new gaskets. Be sure to adjust the float level during reassembly.