2000 RX300 that will start but won't idle. I thought at first it was vapor lock but have been playing with it more and it simply won't idle. I recently had the mass air flow sensor replaced (and finally fixed the check engine light -P0171). Drove a short distance yesterday (< 1 mile) then couldn't get the car to idle when starting it to go to work this morning. As long as I can keep the gas on it it will run it just won't idle. Thougts anyone?

Chris

 

Chris, welcome to Club Lexus. Over the years this problem has occurred at times (even to me) with the RX300 (as recently as a few weeks ago). One possibility is that the there is a disconnected hose usually on the airbox or even a cracked air hose. There is a hose that connects on the backside of the airbox. Barring that, a nasty culprit is the IACV Valve. I go into some steps how to clean this and other possible issues in this thread that I stickyed at the top of the RX300 thread, https://www.clublexus.com/forums/sho...d.php?t=295546

I have also had vapor lock, but the one time it occurred to me after descending almost 8,000 feet in altitude to Veracruz, I merely disconneced and reattached the negative battery cable and ran the RX around the block of the hotel a bit and things were cooking again. However, even after that I had a slightly lower than normal idle (and this was sea level and not high altitude with less oxygen) and ran a bottle of Restore fuel injector cleaner through the gas to clean out the injectors as the gas is not as clean outside of Mexico City or the U.S. border areas, and that got the idle back to around the 750 RPM normal idle.

Let me know if any of these things work.