REMOVAL & INSTALLATION
See Figures 1, 2, 3 and 4
- Disconnect the negative battery cable.
- Remove the air cleaner assembly.
- Detach the electrical connectors from the injector, Idle Air Control (IAC) valve and Throttle Position Sensor (TPS). Remove the wiring harness from the throttle body.
- Tag and disconnect the related vacuum lines from the TBI assembly.
- Remove the throttle cable, and also the transmission detent and cruise control cables as applicable.
- Using a back-up wrench to prevent the fuel nuts from turning on the TBI units, disconnect the fuel inlet and return lines, then remove the fuel tube between the 2 TBI units.
If removing the TBI unit for replacement, perform the following:
- Remove the bolts and nuts from the inlet manifold cover, then remove the TBI unit assembly.
- Place a protective covering over the "swirl" plates located below each throttle plate.
If removing the TBI unit for disassembly, perform the following:
- Remove and discard the throttle rod retaining clip from the front TBI throttle lever stud. A new clip, which is supplied in the service kit, must be used when reassembling the separated front and rear throttle bodies. One throttle rod end bearing is permanently attached to the throttle lever stud of the rear unit, and must not be removed from it. If the throttle rod and bearing assembly needs replacement, the entire rear throttle body must be replaced.
- Remove the TBI-to-cover mounting bolts from the front unit. Then, remove the TBI-to-cover mounting bolts from the rear unit.
- Lift the rear TBI unit off the manifold cover locator pins, and raise it above the front unit. Slide the throttle rod end bearing off the front unit throttle lever stud.
- Remove the front TBI unit and mounting gasket.
- If the TBI unit was removed for replacement, installation is the reverse of the removal procedure. Tighten the retaining bolts and nuts to 10-14 ft. lbs. (14-19 Nm).
If the TBI unit was removed for disassembly, perform the following steps, as applicable.
Reinstalling the units with the original front and rear throttle bodies on the original manifold cover:
- Install new front and rear throttle body mounting gaskets.
- Install the front TBI unit on the manifold cover locator pins. Tighten the mounting bolts to 8-14 ft. lbs. (11-19 Nm).
- Holding the rear unit above the front unit, install the throttle rod end bearing on the front unit throttle lever stud. Install the rear TBI unit onto the manifold cover locator pines. Tighten the mounting bolts to 8-14 ft. lbs. (11-19 Nm).
- Use needle-nose pliers to carefully install a new throttle rod and bearing retaining clip.
- Proceed to the Final Assembly steps.
If you replaced the manifold cover, TBI unit(s) or throttle bodies, perform the following. This section must be followed because replacement of one or more of the assemblies requires throttle valve synchronizing and checking the throttle rod alignment.
- If the tamper resistant plugs covering the throttle stop screws are in place, remove the plugs. Replacement throttle bodies do not have throttle stop screw plugs installed. Use a punch to bet the located, over the center line of the throttle stop screw, for a hole to be drilled. Drill a 5 / 32 in. (4mm) diameter hole plug through the throttle body casting, to the hardened plug. Use a 1 / 16 in. (2mm) diameter punch to drive through the bottom of the drilled hole and knock out the plug.
- If the front TBI unit throttle synchronizing screw has a welded retaining collar, grind off the weld. A replacement throttle body may have a throttle synchronizing screw with a non-welded collar.
- Block possible movement of the throttle lever, as shown in the accompanying figure, relieving the force of the heavy spring against the throttle synchronizing screw, to prevent the levers from coming into contact.
If a lever is not blocked before the throttle synchronizing screw, the screw may be damaged, and reinstallation will be difficult.
- Remove the synchronizing screw and collar, discard the collar and reinstall the screw. Remove the blocking from the throttle lever.
- Install the necessary throttle body mounting gaskets.
- With either throttle body in place, install the throttle rod end bearing on the front unit throttle lever stud.
- Install the other throttle body on the manifold cover locator pins. Tighten the mounting bolts to 8-14 ft. lbs. (11-19 Nm).
- Perform the throttle valve synchronizing or throttle rod alignment check, as necessary.
The following steps are the "Final Assembly" steps.
- Reinstall the connecting fuel tube between the front and rear TBI units. Tighten to 24 ft. lbs. (32 Nm), using a back-up wrench.
- Attach the fuel inlet and return lines, using a back-up wrench on the fuel nuts.
- Connect the throttle cable, and the transmission detent and cruise control cables, if applicable.
- Attach the vacuum lines, as tagged during removal.
- Attach the electrical connectors to the injectors, IAC and TPS. Reinstall the wiring harness on the throttle body.
- Install the air cleaner assembly.
- With the engine OFF , depress the accelerator pedal to the floor and release, checking for free return of the pedal.
See Figure 5
The model 400 TBI preliminary throttle valve synchronizing adjustment may be performed with the assembly on the vehicle, or removed from the vehicle, as a bench procedure.
- Turn both front unit and rear unit throttle stop screws counterclockwise enough to break contact with the related throttle lever tangs.
- Adjust the throttle synchronizing screw to allow BOTH throttle valves to close. The throttle rod end bearing will move freely on FRONT unit throttle lever stud when both valves are closed.
- Turn the FRONT throttle stop screw clockwise slowly unit it makes contact with the throttle lever tang. Turn clockwise 1 / 4 additional turn.
- Turn the REAR throttle stop screw clockwise slowly until it makes contact with the throttle lever tang. Turn clockwise an additional 1 / 2 turn.
- Final adjustments are made with the assembly on the vehicle and the vehicle running.
See Figures 6 and 7
- Actuator the rear unit throttle lever to bring both units to the wide open throttle position by loading the throttle valve as shown. Move the throttle rod toward the front unit casting boss.
- Check the clearance between the shoulder of the stud and the side of the ball surface. Maximum clearance must not exceed 0.20 in. (5.0mm). If the clearance is greater, the replacement assembly (manifold cover, TBI unit, or throttle body) must be exchanged, and the preliminary throttle valve synchronizing adjustment repeated.
- Use needle-nose pliers to install carefully a NEW throttle rod and bearing assembly retaining clip supplied in the replacement kit.
- Move both the front and rear throttle levers through the total throttle travel, locating the throttle valves.
- Check the clearance between the throttle rod and front throttle body casting boss. If the minimum clearance is less than 0.040 in. (1.02mm), replacement assembly must be exchanged. If the minimum clearance is at least 0.040 in. (1.02mm) go to the final assembly.
- If assemblies were replaced, repeat the throttle valve synchronization and throttle valve alignment check.