Stephen Clark

99 Rx300 Low Idle At Startup

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My wife's 99 RX300 sometimes idles very low when started with engine warm. A blip of the throttle generally returns it to the correct idle speed. Seems to happen only when engine is warm. My wife reported that she often has to start multiple times to get it to idle without dying. The car has 82K miles, and is current on all scheduled services. Two oxygen sensors were replaced a couple months ago, but did not affect this problem at all.

I'm thinking ISV needs cleaning, or possibly a temperature sensor is faulty. any opinions? Thanks in advance for your suggestions!

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Do a search on IACV (idle air control valve) Will keep you reading for a while. My suggestion is to REMOVE the IACV and clean it properly. Some guys try the easy way (running some cleaner through with it on the car) and sometimes it works, sometimes for a little while, sometimes not at all. The part can be purchased for $175.-$200. online but isn't THAT bad to remove and clean if you want to save some money. On rare occasions it will need to be replaced.

If a "blip" of the throttle returns it to correct idle, it MAY be a dry and sticky throttle cable or a dirty throttle body instead of bad IACV. The throttle body gets really gunked up from the fumes from the crankcase (PCV valve) and the butterflies in the TB stick easily. Probably wouldn't be a bad idea to clean it. Good Luck!

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Check out this youTube had the same problem in my 2002 RX300 would start but would stall every time at idle when cold was idling at 200-300 rpm. The Idle air control valve has aluminum and steel parts on the butterfly, the aluminum oxidized and was stuck closed wiggled it free idles fine now. check out the video fast forward to 10:30 in the video first part is just diagnosing if the computer is communicating with the IACV.

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I agree that it sounds like classic dirty IACV (idle air control valve) symptoms. I've needed to have mine cleaned every couple of years, since, oh, 80K miles or so (140K now). My Lexus dealer won't clean it -- they'll install a new one for ballpark $400. Ouch! So you'll probably need to use a non-dealer mechanic to get it cleaned. Per other posts, It's not a tough job, and there are Youtube videos that walk you through, but when I tried it I encountered a screw I couldn remove, so now I just have a local shop do it.

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