Notice: The minimum idle speed adjustment is critical to the vehicle's performance and the component's durability. The incorrect minimum idle speed adjustment (too high) will cause the IAC valve pintle to constantly bottom on its seat and result in an early valve failure. If the minimum idle speed is adjusted too low, the vehicle may not start in cold weather or may stall during a warm-up.
Important: Only adjust the minimum idle speed when installing a replacement throttle body.
The idle stop screw regulates the minimum idle speed of the engine. On an original equipment throttle body, the idle step screw is adjusted at the factory, then is covered with a plug in order to discourage an unnecessary readjustment.- Check the controlled idle speed. Perform idle air control system check first.
- Set the parking brake and block the drive wheels.
- Start the engine. Bring the engine to the normal operating temperature (85°-100°C). Turn the engine OFF.
- Remove the air cleaner, the adapter, and the gaskets. Check that the throttle lever is not bound by the throttle cable.
- With the IAC valve connected, ground the diagnostic terminal at the Data Link Connector (DLC).
- Turn ON the ignition. Do not start engine. Wait at least 45 seconds. This allows the IAC valve pintle to extend and seat in the throttle body.
- With ignition ON, engine stopped, test terminal still grounded, disconnect IAC valve electrical connector. (This disables IAC valve in seated position.) Remove ground from diagnostic terminal.
- Connect a scan tool to the DLC. Place in open mode.
- Start the engine. With the transmission in neutral, allow the engine RPM to stabilize.
- Check the RPM against specifications (450-550 RPM). Disregard the IAC counts on scan tool with the IAC disconnected. If the engine has less than 500 miles or is checked at altitudes above 1500 feet, the idle RPM with a seated IAC valve should be lower than values above.
- If the minimum idle speed is within specifications, no further check is required.
- If the minimum idle speed is not within specifications, perform the following procedures:
| 12.1. | If present, remove the stop screw plug (1) by piercing it with an awl, then applying leverage The screw (2) is covered in order to discourage unauthorized adjustments. |
| 12.2. | With engine at normal operating temperature (85°-100°C), adjust the stop screw in order to obtain the nominal RPM per specifications with a seated IAC valve. |
| 12.3. | Turn the ignition OFF. Reconnect the IAC valve electrical connector. |
| 12.4. | Disconnect the scan tool. |
| 12.5. | Use a silicon sealant or the equivalent in order to cover the stop screw hole. |
| 12.6. | Install the air cleaner, the adapter, and the gaskets. |
Clean and Inspect
Notice: Do not subject the throttle body assembly which contains the following
components to a strong solvent or cleaner bath:
• The Throttle Position (TP) sensor • The Idle Air Control (IAC) valve • The fuel meter cover assembly • The fuel injectors • The sealed ball bearings • The shock absorber • The lever with the sealed needle bearing • The governor throttle assembly (the cover plate) which includes
the drive motor and the shock absorber
- Clean all metal parts thoroughly. Blow dry with shop air. Free all fuel and air passages of dirt or burrs.
- Inspect the mating casting surfaces for damage that could affect gasket sealing.
Important: Clean in a cold immersion cleaner such as Carbon X (X-55) or the equivalent all TBI component parts with the exception of those observed below.
Thread-Locking Compound
Notice: Do not use a higher strength locking compound than recommended when precoating the screws. Doing so could make removing the screw extremely difficult or result in damaging the screw head.
The service repair kits contain a small vial of thread-locking compound with directions for use. If the material is not available, use Loctite 262 or the equivalent.
