Hello all,

I want to know what causes the engine RPM to raise a bit when you start the AC?
Is there a choke system?
And where is it located on 1998 LS400?

I'm suspecting that i might have a problem with it cause my engine's RPM is not up and down with the AC compressor switching as is used to be which causes the AC to be less cold when in long stops.

Thank you for your help.

 

what is the function of this part 25860‑50110 (VALVE ASSY, VACUUM SWITCHING No.1) ? is it the choke that i'm asking about?

 

98 LS400 does not have any choke. The ECU controls the idle speed. When the AC is on, the throttle valve is open a bit more by the motor controlled by the ECU to get a better performance of the AC.

When the throttle body is clogged too much, the function is not done well enough. I suggest you to clean the throttle body. Search the forum and you can find the way how to do it. Sometimes the throttle body itself is partially broken (the motor, the sensor not functioning properly), you would have similar problem. But in that case, the engine check light turns on in most of the case.

 

Thank you for your reply, really appreciated.

Will do as you said.