Toyota Celica/Supra 1971-1985 Repair Guide

Dashpot (DP) System


The Dashpot (DP) system is used on most Supras and all Celicas with fuel injection and manual transmission. The system is used primarily to reduce HC and CO emissions upon deceleration. When decelerating, the dashpot opens the throttle slightly more than when at idle. This causes a more efficient burning of the air/fuel mixture.


See Figures 1, 2 and 3

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Fig. Fig. 1: Run the engine to 2500 rpm (3000 rpm on Supra) and pinch the hose

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Fig. Fig. 2: Adjusting the Celica dashpot

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Fig. Fig. 3: Adjusting the Supra dashpot

  1. Run the engine until it reaches normal operating temperature.
  3. Check the idle speed mixture and ignition timing. Adjust if necessary.
  5. Run the engine at 2500 rpm (3000 rpm on the Supra) and pinch the vacuum hose between the dashpot and the VTV.
  7. Release the throttle and check that the dashpot holds the engine speed at 2000 rpm.
  9. Adjust the dashpot to the proper speed (if necessary) as illustrated.
  11. Release the pinched vacuum hose and check that the engine returns to idle speed within 1 second.