GM Storm/Spectrum 1985-1993 Repair Guide

Throttle Body

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REMOVAL & INSTALLATION



See Figure 1

  1. Disconnect the negative battery cable.
  2.  
  3. Partially drain the engine cooling system to a level below the throttle body coolant hoses.
  4.  
  5. Tag and disconnect the vacuum connections from the throttle body.
  6.  
  7. Unplug the IAC valve and TPS wiring from the terminals.
  8.  
  9. Disconnect the air cleaner-to-throttle body duct from the throttle body. If necessary, remove the duct completely for better access.
  10.  
  11. Disconnect the coolant hoses from the fittings on the bottom of the throttle body.
  12.  
  13. Disconnect the throttle and, if applicable, cruise control linkage.
  14.  
  15. Remove the throttle body attaching bolts, then remove the throttle body and flange gasket from the intake. Discard the old flange gasket.
  16.  

To install:
  1. Thoroughly clean the gasket mating surfaces, but be careful not to score the machined aluminum surfaces.
  2.  
  3. Install the throttle body assembly using a new gasket. Secure using the mounting bolts and tighten to 16 ft. lbs. (22 Nm).
  4.  
  5. If removed, install the power steering brace and tighten.
  6.  
  7. Install the throttle linkage, and if equipped, the cruise control cable. Make sure the cable(s) do not hold the throttle open when the accelerator pedal is released.
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  9. Connect the coolant hoses to the throttle body fittings.
  10.  
  11. Install the air cleaner-to-throttle body duct.
  12.  
  13. Install the wiring harness connectors to the IAC valve and TP sensor terminals.
  14.  
  15. Install the vacuum connections.
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  17. Refill the engine cooling system.
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  19. Connect the negative battery cable, then start the engine and check for leaks.
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Click image to see an enlarged view

Fig. Fig. 1: Exploded view of the throttle body assembly

ADJUSTMENTS



Idle Speed Check

The minimum idle speed is preset at the factory and requires no periodic adjustment. The factory adjustment should not be tampered with.

  1. If there is problem with high idle speed, the most likely cause is a vacuum leak. Check all vacuum hoses and connections. Make sure the throttle body is properly mounted and the gasket is intact.
  2.  
  3. If no vacuum leaks are found, perform the IAC valve functional check. Refer to the diagnostic charts in Emission Controls of this repair guide. Also, make sure IAC valve pintle position is not lost which could occur if the battery cable was disconnected. Refer to the IAC valve Idle Learn procedure, later in this section.
  4.  
  5. If the minimum throttle position is still suspect, continue with the procedure. Block the drive wheels and apply the parking brake, then place the transaxle in N .
  6.  
  7. Connect a suitable scan tool to the ALDL/DLC. Refer to Emission Controls of this repair guide for information regarding the ECM and self-diagnostics.
  8.  
  9. Start the engine and allow it to idle until normal operating temperature is reached (about 90°C) and the engine enters Closed Loop operation.
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  11. If equipped with an automatic transaxle, shift to D , then back to N .
  12.  
  13. Select the power steering pressure switch input on the scan tool. Make sure the A/C and ALL accessories are turned off. The power steering pressure switch reading should be OFF or NORMAL indicating that engine load is at minimum. If reading is incorrect, diagnose and repair and possible faulty pressure switch circuit.
  14.  
  15. Select IAC valve display on the scan tool and monitor IAC valve counts. If between 5-45 counts, the minimum throttle position is acceptable. It is important that the idle speed be stabilized before attempting to read counts.
  16.  
  17. If IAC counts are too low, check for a vacuum leak missed earlier at the hoses, throttle body, and intake manifold. Check for a damaged throttle lever and correct, as necessary. If no causes can be found for the excessive air flow into the intake, the throttle body must be replaced.
  18.  
  19. If IAC counts are too high, check for a damaged throttle lever or air flow restriction by the throttle valve. If no problem is evident, disconnect the inlet duct from the throttle body and use a carburetor cleaner (which does not contain Methyl Ethyl Ketone) along with a shop towel to clean residue from the throttle body bore. Recheck the IAC counts and, if still too high, replace the throttle body.
  20.  

 
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