The Air Bypass Solenoid (Figures 1, 2 and 3) is used to control engine idle speed and is operated by the Electronic Engine Control (EEC) processor.

Three types of air by-pass valves are released for use (Figures 1, 2 and 3):
> Hitachi (Figure 1)can be identified by a silver metal housing. It can be cleaned. (Refer to Service Manual).
> Hitachi(Figure 2) can be identified by an external vent/filter. It cannot be cleaned.
> Nippondenso (Figure 3) can be identified by a black plastic housing. Do not use cleaning solvent on this valve. To service this valve, replace it.

The valve allows air to bypass the throttle plates and controls:
> Cold engine fast idle
> No touch start
> Dashpot
> Over temperature idle boost
> Engine idle load correction

Owner caption March 2005 · Photo 297 of 980