Toyota Camry: High idle - intermittent

I have a Dec 1999 Toyota Camry Conquest with a V6 3L engine (1MZ-FE),
automatic, 135,000km. Sometimes (10-20% of the time), the idle sticks
high (900rpm). Most of the time it idles at 700rpm.

This high idle problem happened recently (3 weeks ago). It is not
related to AC, engine well warmed up, temperature gauge display
normal. Tapping gas padel does not set it back. If the idle is at 700,
change from neutral (N) to drive (D) is smooth. If it idles high
(900), N to D change gives a forward kick and the idle drops down to
700 (when in D).

When it idles high, transission from first gear to second also gives a
forward kick.

Firstly, I have suspected the IAC. After extensive searching of the
internet, it looks to me that the IAC problem is more to do with low /
unstable idle.

Any relevant suggestions about the possible source of problem or
solution would be highly appreciated.

Regards,


Sam Yang
au

au (Sam Yang) wrote in message news:<google.com>... 
Not familiar with your particular engine, but generally speaking, the
carb cleaner container needs to specifically state "safe for emission
controls" or something similar -- if not explicitly mentioned -- find
another brand.
Also, thry spraying the carb cleaner into the air inlet for the IAC
valve with the engine idling, keeping it running by moving the
butterfly valve at the throttle body to work the cleaner through the
valve.
When cleaning the IAC valve with the engine off, I have found the
idling problems return much sooner.