HonakerAuto

Created an account just to reply to this thread! Hopefully the info will be useful to someone. :D We have a customer's vehicle here ('93 LS400) that has both issues (smoking and power steering fluid loss). This particular one has had the P.S. pump replaced by other shops three times already in an effort to remedy its persistent leak, but apparently nobody else that had worked on it knew to check that valve. By the way, the valve in question is not the idle speed control valve as the O.P. had described. Toyota lists it as an "idle-up" valve, but this particular part does not regulate the engine's idle speed. The valve that does that (the ISC itself) is actually on the side of the throttle body. What it really does is sample manifold vacuum and use that to command the pump to boost the steering fluid pressure as vacuum increases, so as to give more responsive steering at higher speeds. The problem is that when it fails internally the fluid passing past it on the pump side gets sucked into the intake, simultaneously creating both the smoking and P.S. fluid loss problems. (Worse, if you inhale enough fluid into the intake there's always the risk of a hydrolock and corresponding engine damage.) The part shows on our copy of Mitchell OnDemand as costing about $200 (dealer list), the dealer I called showed it as about $100 list, and there's no labor entry for it but given its location expect to have to pay slightly above pump R&R time (which runs about 3 hours for the '93 LS400) to have it replaced if you're not mechanically inclined enough to do so yourself. It's not available though aftermarket channels so you'll need to hit up your Lexus dealer for it. Hope all of this helps in some manner!