On the Multi-port Fuel Injection (MFI) system, each injector is mounted directly into the head at the cylinder. On this system, the throttle body controls the amount of air entering the intake system, but does not meter fuel in any way.
REMOVAL & INSTALLATION
The throttle body for each of the MFI engines is slightly different. The procedure below is general and may require slight alteration of sequence depending on the engine.
See Figures 1 and 2
- Disconnect the negative battery cable.
- Drain the coolant, at least to a level below the intake manifold.
- Disconnect the main air intake duct from the throttle body.
- Label and disconnect the vacuum and breather hoses running to the throttle body. Take care that clamps are not bent or distorted during removal.
- Disconnect the accelerator cable and the cruise control cable if so equipped.
- Label and disconnect the coolant hoses running to the throttle body.
- Follow each wire running from the throttle body. Label and disconnect each at its connector. Most of the wiring harnesses have connectors at some distance from the throttle body. Loosen, release or remove any clips or brackets holding the throttle body harnesses in place.
- Carefully remove the four nuts and bolts holding the throttle body to the manifold. The throttle body may use bolts of two different lengths; take careful note of each bolt's position.
- Lift the throttle body away from the manifold and handle it carefully. Place it in a protected location.
- If the unit is being replaced, compare the old and the new ones. Look for any components which need to be transferred from the old unit. The throttle plate area may be cleaned with a spray cleaner, but must be completely dry before installation. Disassembly of the throttle body is not recommended.
- Make sure that all remains of the old gasket are removed from both the manifold flange and the base of the throttle body. Place a new gasket on the manifold and hold the throttle body in place.
- Install the four nuts and bolts finger-tight. Make certain the bolts are in the correct holes by length. Tighten the bolts evenly, alternating from bolt to bolt, in small increments. The bolts must draw down evenly, creating an airtight seal against the gasket.
For all engines, tighten the nuts and bolts to the following torque figures. Do NOT overtighten these bolts. The figures are:
1990-91 2.4L Engines-11-16 ft. lbs. (15-22 Nm)
- Reconnect the wiring to the harnesses. Secure, tighten or reinstall any wire clips or retainers. The harnesses must be kept clear of moving or hot surfaces.
- Install the coolant hoses, making sure each is properly clamped to its port.
- Install the accelerator cable and cruise control cable if so equipped. Adjust the cable to the correct tension and make certain the locknuts or bracket bolts are secure.
- Connect the vacuum hoses. Examine the end of each and replace any showing signs of cracking or hardening.
- Install the main air duct and connect the breather tubes.
- Refill the coolant to the proper level.
- Connect the negative battery cable.
THROTTLE CABLE ADJUSTMENT
Models Without Cruise Control
See Figures 3, 4 and 52.4L ENGINE
Adjust the accelerator cable with no load on the engine or electrical system
- Turn the air conditioning and lamps off.
- Warm the engine until stabilized at idle.
- Confirm that idle rpm is at the prescribed rpm.
- Stop the engine (turn the ignition switch OFF.
- Confirm that there are no sharp bends in the accelerator cable.
- Check the inner cable for the correct amount of slack. The slack should be 0.04-0.08 in. (1-2mm) for a manual transmission, and 0.12-0.02 in. (3-5mm) for an automatic transmission.
If there is too much or not enough slack, adjust the play by the following procedure:
- Turn the ignition switch to the ON position and hold the switch in that position for 15 seconds (with the engine not running).
- Loosen the adjusting nut so that the throttle lever is free. Turn the accelerator adjusting nut to the point where the throttle lever just starts moving, then back off one turn and lock the adjusting nut with the locknut.
- The accelerator cable free-play should now be the standard setting.
- Confirm that the throttle cable stopper touches the air idle control actuator.
- Check that there are no sharp bends in the routing of the accelerator cable.
- Check that the throttle link is touching the fixed SAS (stopper).
- Loosen the adjusting bolts on the intake manifold plenum, then secure the outer cable so that the free-play of the inner cable will be the standard value of 0.04-0.08 in. (1-2mm).
If there is excessive play in the accelerator cable, the vehicle speed drop ("undershoot") when climbing a slope. If there is no play (excessive tension) in the accelerator cable, the idling speed will increase.
- After adjustment confirm that the throttle valve fully opens and closes by operating the pedal.
Models With Cruise Control See Figures 6, 7 and 8
- Depress the accelerator pedal and check to be sure that the throttle lever moves smoothly from fully open to fully closed.
If there is excessive sagging of the inner cable of the accelerator cables A and B, or if there is no sagging at all, first check the arrangement and placement of the cable, then adjust as described below.
- Idle the engine to warm it up to a steady rpm.
- Confirm that the idle rpm matches the specified rpm. In this case the specified rpm is 650-850 rpm (2.4L engines) or 600-800 rpm (3.0L Engines) at idle.
- Stop the engine and remove the cover of the actuator.
- Loosen the lock nuts of the accelerator cables A and B and let the inner cables sag.
- While keeping lever P and the stopper in contact with each other, turn the adjusting nut (in the direction that causes the outer cable to become longer) until just before the lever P begins to operate, then turn the nut 1 / 2 turn back and secure it with the locking nut. This operation will ensure that the free-play of the accelerator cable A is correctly adjusted. The standard value of free-play for cable A is 0-0.04 in. (0-1mm).
- In order to get the play of accelerator cable B (the distance C, between levers C and P) to the standard value, alter the adjusting nuts of the throttle body and adjust. The standard value for accelerator cable B is 0-0.08 in. (0-2mm).
If there is excessive play of the accelerator cables, the vehicle speed drop ("undershoot") when climbing a slope. If there is no play (excessive tension) of the cables, the idling speed will increase.
- After adjusting the cables, operate the accelerator pedal, turn the lever steadily and make sure that the throttle lever is being activated. Also move the actuator, turn the lever steadily and make sure that the throttle lever is being activated.
- Install the actuator cover.