Toyota Pick-ups/Land Cruiser/4Runner 1970-1988

Dash Pot (DP) System

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OPERATION



See Figures 1, 2, 3, 4 and 5

The dash pot (DP) system is used on all fuel injected models with manual transmissions and all 1985-87 carbureted models with automatic transmissions. The system is used primarily to reduce HC and CO emissions upon deceleration. When decelerating, the dash pot opens the throttle slightly more than when at idle. This causes a more efficient burn of the air/fuel mixture.



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Fig. Fig. 1: Dashpot system component layout and vacuum diagram-1984-86 22R-E and 22R-TE engines



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Fig. Fig. 2: Dashpot system component layout and vacuum diagram-1987-88 22R-E and 22R-TE engines



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Fig. Fig. 3: Dashpot system component layout and vacuum diagram-3VZ-E engine



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Fig. Fig. 4: Dashpot system component layout and vacuum diagram-3F-E engine



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Fig. Fig. 5: Dashpot system component layout and vacuum diagram-1985-87 22R engine

SERVICE



See Figures 6, 7, 8 and 9

Fuel Injected Engines
  1. Run the engine until it reaches normal operating temperature.
  2.  
  3. Check the idle speed and ignition timing. Adjust if necessary.
  4.  
  5. Remove the cap and filter from the dash pot on the 3VZ-E.
  6.  
  7. Run the engine at 2500 rpm and pinch the vacuum hose between the dash pot and the VTV. On the 3VZ-E, plug the VTV hole.
  8.  
  9. Release the throttle and check that the dash pot holds the engine speed at 2000 rpm.
  10.  
  11. Adjust the dash pot to the proper speed (if necessary).
  12.  
  13. Release the pinched vacuum hose and check that the engine returns to idle speed within 1 second.
  14.  

Carbureted Engines
  1. Run the engine until it reaches normal operating temperature.
  2.  
  3. Check and adjust the idle speed and ignition timing as previously detailed.
  4.  
  5. Open the throttle valve until the throttle lever separates from the end of the dash pot.
  6.  
  7. Gradually release the throttle valve and check that the dash pot set speed is 3,000 rpm when the throttle lever contacts the end of the dash pot.
  8.  
  9. To adjust the set speed, loosen the locknut and rotate the dash pot.
  10.  



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Fig. Fig. 6: Dashpot filter-3VZ-E engine



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Fig. Fig. 7: Plug the VTV hole-3VZ-E engine



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Fig. Fig. 8: Adjusting the dashpot-3VZ-E engine



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Fig. Fig. 9: Dashpot adjusting screw-1985-88 22R-E and 22R-TE engines

 
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