Fast Idle - Too Fast, Too Long

[artbuc]

My 99 RX is idling too fast and too long. I keep it in an unheated garage which may drop to 40-45 degrees on a cold night. When I start it, it idles at 1800 and doesn't come all the way down until I drive it a few miles and the engine comes up to normal temp. At that point all is well.

Any tips on what to check first? Seems like it could be the IACV or the engine temp sensor.

[bowtie3]

My 99 RX is idling too fast and too long. I keep it in an unheated garage which may drop to 40-45 degrees on a cold night. When I start it, it idles at 1800 and doesn't come all the way down until I drive it a few miles and the engine comes up to normal temp. At that point all is well.

Any tips on what to check first? Seems like it could be the IACV or the engine temp sensor.

My wife's 2000 RX300 [ 56,000 miles ] did the same thing, plus high idle all of the time. It really banged/jerked when putting it into gear. [ Can really screw-up a transmission ] Took it to the Lexus dealer TWICE in 2 weeks for the problem. Was told there is NO PROBLEM FOUND! Finally after about 3 weeks the " check-engine " light came on. The dealer THEN was able to diagnose the problem; THROTTLE POSITION SENSOR. It was replaced under the Certified Warranty. [ Problem solved ] It seems that the ONLY way to correctly diagnose a problem is by computer; the service techs didn't have a clue. I guess the dealer doesn't keep service techs long enough for them to be acquainted with the vehicle's problems. I stopped by the Toyota dealer to consult with one of the techs there and he told me " it's a common problem ". So is the gas knock caused by the poor-designed knock-sensor harness location.