Throttle Body Assembly Removal and Replacement
Throttle Body Assembly Model B110:
Throttle Body Removal:
CAUTION:
^ The throttle bore and valve deposits may be cleaned on the vehicle, using carburetor cleaner and a parts cleaning brush. Do Not use a cleaner that contains Methyl Ethyl Ketone. It is an extremely strong solvent, and not necessary for this type of deposit.
^ The throttle body metal parts may be cleaned following disassembly, in a cold immersion-type cleaner such as GM X-55 or equivalent.
^ The throttle position sensor (TPS) and idle air control (IAC) valve should NOT come in contact with solvent or cleaner, as they may be damaged.
NOTE: An eight digit part identification number is stamped on the bottom of the throttle body casting next to the coolant cover. Refer to this number if servicing, or part replacement is required.
REMOVAL:
1. Disconnect the negative battery cable.
2. Partially drain the radiator, to allow the coolant hoses at the throttle body to be disconnected.
3. Remove the air inlet duct at the throttle body, and crankcase vent pipe at the valve cover grommet.
4. Disconnect the TPS and IAC valve electrical connectors.
5. Remove the idle air pipe.
6. Disconnect the vacuum harness connector from the throttle body.
7. Disconnect the throttle, T.V. (transmission control), and cruise control cables.
8. Disconnect the coolant hoses from the throttle body.
9. Remove the throttle body attaching bolts.
10. Remove the throttle body assembly and flange gasket, discard gasket.
11. Clean gasket sealing surfaces.
CAUTION: Use care when cleaning old gasket material from machined aluminum surfaces. Sharp tools will damage sealing surfaces.
ASSEMBLY:
1. Install throttle body assembly, with a new gasket, on the air plenum.
2. Insert the throttle body attaching bolt and tighten to 27 Nm (20 lb.ft).
3. Connect the coolant hoses to the throttle body.
4. Reconnect the throttle, T.V., and cruise control cables.
NOTE: Make sure that the throttle and cruise control cables do not hold the throttle open.
5. Connect the vacuum harness connector.
6. Connect idle air pipe.
7. Connect TPS and IAC valve electrical connectors.
8. Install the air inlet duct to the throttle body, and crankcase vent pipe to the valve cover grommet.
9. Refill the radiator.
10. Connect the negative battery cable.
NOTE: Adjust TPS, IAC valve, and the idle stop screw.
^ The idle stop screw is used to regulate minimum idle speed of the engine. On original equipment throttle bodies, it is adjusted at the factory, then covered with a plug to discourage unnecessary adjustment.
^ On replacement throttle bodies, the idle stop screw is not adjusted and is not covered with a plug.
PROCEDURE:
1. Back the idle stop screw out until an air gap between the screw and the throttle lever can be seen by looking downward from above the throttle body.
2. Turn the stop screw in until it just contacts the throttle lever.
3. Turn the stop screw in 1 1/2 turns further.
4. Block the drive wheels, and apply the parking brake.
5. Connect a SCAN tool to the ALDL connector.
6. Turn the ignition switch to the ON position.
7. Select TPS voltage display on the SCAN tool, and adjust the Throttle Position Sensor (TPS) to obtain 0.55 +/- 0.1 volt.
^ Tighten the attaching screws just enough to hold the TPS in place. Readjustment may be required following minimum idle speed adjustment.
8. Select "Field Service Mode" on the SCAN tool (refer to SCAN tool instructions). This will cause the IAC valve pintle to seat in the throttle body (closing the air passage). Wait at least 45 seconds, disconnect the IAC valve connector, then exit "Field Service Mode."
9. Shift the transmission to Park (A/T) or Neutral (M/T). Start and run the engine until it reaches normal operating temperature, and "Closed-Loop" operation as read on the SCAN tool.
^ It may be necessary to hold the throttle slightly open to maintain an idle.
10. Select IACV on SCAN tool, and read IACV counts.
NOTE: Engine should be operating in "Closed Loop."
^ Accessories (A/C, rear defogger, etc.), and engine cooling fan "OFF.
^ Make sure the throttle and cruise control cables do not hold the throttle open.
^ With the engine stabilized, the IAC valve position should be 10 to 15 counts.
11. If the IAC counts are out of the acceptable range, the adjustment may be changed as follows:
^ More throttle valve opening = lower IAC valve counts.
^ Less throttle valve opening = higher IAC valve counts.
^ If it is necessary to change the adjustment more than one half turn either way, other causes of incorrect idle speed should be investigated as previously mentioned.
12. Turn the ignition OFF.
13. Connect the IAC valve.
14. Turn the ignition to the ON position, and recheck the TPS voltage on the SCAN tool. Adjust if necessary, to obtain 0.55 +/- 0.1 volt.
^ Tighten the TPS attaching screws to 2.0 Nm (18 lb.in). Make sure the adjustment did not change after tightening screws.
15. Turn ignition OFF for ten seconds (this will reset the IAC valve pintle position).
16. Start the engine and check for proper idle operation.
17. Disconnect the SCAN tool.
18. Remove the block from under the drive wheels.