Honda Accord/Prelude 1984-1995 Repair Guide

Idle Speed

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ADJUSTMENT



See Figure 1

Minor adjustments of warm idle speed may be needed as a result of an ignition tune-up or other maintenance procedures. In general, engine idle speed adjustment does not change by itself; if the idle is too low or a stalling problem is present, search out the real cause instead of hiding it with a higher idle speed.



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Fig. Fig. 1: Tune-up specifications can be found listed on the underhood emissions label

Carbureted Engines

See Figures 2 and 3

On carbureted engines, the idle should be checked with the engine at normal operating temperature and the fast idle system fully disengaged. Connect a tachometer to the vehicle following the manufacturers instructions.

Adjustments are made at the throttle stop screw on the carburetor. This is a mechanical adjustment which simply opens or closes the throttle plate a small amount, thus altering the idle speed. On Accords, the throttle stop has a knurled plastic knob to make adjustment easier. The knob, however, is located on the firewall side of the carburetor and may be difficult to reach. The spring on the adjuster also makes the knob a bit stiff to turn.



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Fig. Fig. 2: Accord throttle adjusting screw; 1986-89 models shown, 1984-85 models are similar

Preludes, with their dual-carb arrangement, use a vertically placed screw acting on the throttle linkage. The screw is located between the two carburetors on the linkage.



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Fig. Fig. 3: Prelude throttle stop screw

Particularly on Preludes, but on Accords also, be very certain that you have found the proper screw before making adjustments. Any linkage screw sealed with a dot of paint (usually yellow) is NOT to be altered. These are factory set and, in some cases, are not resettable in the field.

Fuel Injected Engines
1985 ACCORD

See Figure 4

  1. Start the engine and allow it to reach normal operating temperature. The cooling fan must come on at least once.
  2.  
  3. Connect a suitable tachometer using the manufacturer's instructions.
  4.  
  5. Check idle speed with all accessories OFF.
  6.  

To prevent the idle control system from operating, pinch off vacuum hose number "27."

  1. Idle speed should be 700-800 rpm (in neutral). Adjust the idle speed, if necessary, by turning idle adjusting screw.
  2.  



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Fig. Fig. 4: Idle adjustment screw on 1985 Accord

  1. Check the idle controller boosted speed with the air conditioning ON. Idle speed should be 750-850 rpm (in neutral).
  2.  
  3. Adjust idle speed, if necessary, by turning the air conditioning idle adjusting screw.
  4.  

1986-95 ACCORD AND PRELUDE

See Figures 5, 6 and 7

  1. Start engine and warm up to normal operating temperature; cooling fan will come on twice.
  2.  
  3. Connect a tachometer following the tool manufacturer's instructions.
  4.  
  5. On 1986-87 Accords and 1984-87 Preludes, disconnect the upper vacuum hose to the idle control solenoid valve (between the valve and intake manifold) from the intake manifold. Cap the end of the hose and intake manifold.
  6.  
  7. On 1988-95 vehicles, unplug the Electronic Air Control Valve (EACV) connector.
  8.  
  9. With all accessories OFF, check the idle speed. Compare the idle speed to the specification found on the underhood sticker or to the tune-up specifications chart (in this section). If necessary, adjust by turning the idle adjusting screw.
  10.  
  11. Turn the ignition switch OFF .
  12.  
  13. Engage the EACV connector, then remove either the CLOCK or BACK UP fuse in the underhood fuse box for at least 10 seconds; this resets the ECU.
  14.  
  15. Check the idle speed with heater fan switch on HI and the air conditioning ON. Idle speed should be 700-800 rpm (in neutral). Adjust the idle speed, if necessary, by turning the adjusting bolt on the air conditioning idle boost valve.
  16.  
  17. After adjustment, connect the idle control solenoid valve vacuum hose.
  18.  
  19. After adjusting the idle speed on automatic transaxle models, check that it remains within specified limit when shifted in gear.
  20.  
  21. Check the idle speed with all accessories ON and the air conditioning OFF. Idle should remain at 700-800 rpm.
  22.  



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Fig. Fig. 5: On 1986-87 Accords and 1984-87 Preludes, disconnect the upper vacuum hose to the idle control solenoid valve



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Fig. Fig. 6: On 1988-95 vehicles, unplug the Electronic Air Control Valve (EACV) connector



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Fig. Fig. 7: The idle speed adjusting screw is located on the throttle body

 
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