JAB

Mechanic thinks that my 1999 RX300 with 145k may need a new idle air control valve motor to correct the intermittent problem I am having in that when cold, car will not idle. $600 parts and labor to replace. Anyone with any experience with this issue?

Lexmex

What other issues are you noticing besides what you mentioned?

While the IACV valve could be a likely culprit, I have some doubts since this is not occurring all of the time, does not mean that it could not. Usually, I find that the idle problems occur with the hot weather. If the cold weather is kind of strange weather anomoly, that can screw with the ECM and sometimes throw an idle, but that is not a direct result of a bad IACV.

How much are they charging you for the actual parts?

JAB

I did not mean cold weather; I meant if the motor is cold, i.e. not recently running.

Lexmex

OK

A few other things I would check to eliminate are the air filter (clean/dirty?) and also the MAF sensor being clean.

One thing I would try (and this is safe since you are not driving around) is to remove the air filter out of your air box and see if the vehicle starts and/or have idle problems. Sometimes, just a tiny variation in airflow is enough to trigger an ECM problem and cause idle problems.

If nothing else is found, it likely does point to the IACV Valve.

Occasionally, I get, with hot weather, an idle problem or two with my RX300. I then pull the EFI fuse and or the battery cable and then wait a few seconds after starting the vehicle to see if the RPM is at 750 or higher.

jdimegs143

My 01' rx300 started having idling problems, it kept shutting off if i took my foot on the gas, it started acting up during a heat wave in my area and commonly that can cause it to start happening.....after talking to the dealer they pointed to the IVAC/throttle body, new parts $350+$100/hr. for labor; after doing some research I found this was a common problem with this vehicle and was easily fixable for practically a couple bucks!! visit the link

http://us.lexusownersclub.com/forums...howtopic=30723

other than basic tools, you will need a high powered air hose

this is a step by step instruction from another user that completed the repair, it shows great pics and information...BUT after attempting to do it myself, I found a more simpler approach and ended up with the same out come, a great running rx like new,,,,,so here's the deal, follow the steps up to #4 complete step #4 BUT do not take off the black electic cable (it's un nessecary if you do this my way) after all the 4 steps are done, (make sure you read step 4 clearly and don't lose the washer, thats when you spray a decent amount of Carb/Throttle cleaner (Oxygen Sensor safe only please!) into both the intakes, you'll have to hold down the switch that works the cable that opens and shuts the intakes (it helps if you have someone else hold it while you are cleaning) once it's held down, continue to spray the cleaner in, you will probably see black stuff pour out of the bottom of the IACV (where the hose was previously connected that you took off) now use a high pressure air hose and blow out both intakes, basically you are blowing out all the crap in there that the cleaner dissolved repeat steps over and over spraying more cleaner until you see no more black,,,,then throughly clean both intakes (again you need to hold down that switch to keep them flipped open) get in as far as you can with a clean rag, most likly you will get a decent amount of black deposit, I DID! after all is clean, put everything back in reverese order, and don't forget to put the washer back on.
note* you may need to drive it a bit to have it run perfectly arond the block a couple times would be sufficient. I hope all this helps, also my rx has 55,000 on it, and it seems to be around this time is when most have this problem good luck!