Quest 1995-1996

Adjustments

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Idle Speed



The engines covered by this manual utilize sophisticated fuel injection systems in which an engine control computer utilizes information from various sensors to control idle speed and air/fuel mixtures. The engine control computer controls idle speed through the use of an idle air control (IAC) valve, which is not adjustable. There is, however, a reference (base) idle speed adjustment. Although periodic adjustment is not necessary, base idle speed should be checked after the completion of some repairs, such as throttle body replacement. Base idle speed should NEVER be adjusted to compensate for idle speed variations, rough idle, hesitation, or other running problems. These problems require further troubleshooting to isolate their cause.

Base Idle Speed Adjustment

When checking base idle speed, observe the following conditions:



All lights and accessories must be turned off.
 
The engine should be warmed up to normal operating temperature.
 
The front wheels should be pointed straight ahead.
 
Make sure that the radiator cooling fan has stopped before checking idle speed.
 
The transmission must be in park (P) or neutral (N).

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Fig. Base idle speed adjustment screw location-1993-98 3.0L engine



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Fig. Base idle speed adjustment screw location-1999-00 3.3L engine

 

  1. Start and run the engine at about 2000 rpm for about two minutes.
  2.  
  3. Turn the engine OFF and disconnect the throttle position sensor harness connector, located at the throttle body.
  4.  
  5. Connect a tachometer, following the manufacturer-s instructions.
    CAUTION
    Keep away from moving engine parts such as the cooling fan and drive belts. Do not wear loose clothing or jewelry while under the hood of the car with the engine running.

  6.  
  7. Start the engine and rev it 2 or 3 times to 2000-3000 rpm. Allow the engine to return to idle for a minute.
  8.  
  9. Check the engine idle speed. Idle speed should be 650-750 rpm. If not, turn the base idle speed adjusting screw to obtain the specified rpm.
  10.  
  11. Turn the engine OFF . Reconnect the throttle position sensor harness connector.
  12.  
  13. Start the engine and rev it 2 or 3 times to 2000-3000 rpm. Allow the engine to return to idle for a minute.
  14.  
  15. Check the engine idle speed. Idle speed should be 700-800 rpm. If not, determine the cause and make the necessary repairs or adjustments.
  16.  
  17. Turn the engine off. Disconnect the tachometer.
  18.  

 
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