Lexus SC300 / Lexus SC400. Service manual - part 742

As with the rack and pinion type steering, preload is very important. If the preload is not correct, it could
result in such trouble as steering wheel play or shimmy or lack of durability, so always make sure that it
is correct.

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STEERING

POWER STEERING

SR–107

IDLE–UP DEVICE

The pump produces the maximum fluid pressure when the steering wheel is turned fully to the right or left
and, at this time, there is a maximum load on the pump which causes a decrease in engine idle rpm. To
solve this problem, vehicles are equipped with an idle–up device which acts to raise the engine idle rpm
whenever there is a heavy load on the pump.
On EFI engines, when the piston of the air control valve is pushed by fluid pressure, the air valve opens
and the volume of air by–passing the throttle valve is increased to regulate engine rpm.

The idle–up device functions to raise engine idle rpm when pump fluid pressure acts on the air control valve,
installed to the pump body, to control the flow of air.

SR–108

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STEERING

POWER STEERING

PREPARATION
SST (SPECIAL SERVICE TOOLS)

SR0FV–05

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STEERING

POWER STEERING

SR–109

SR–110

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STEERING

POWER STEERING