Es300 Idle Problem Re-Surfaced After Major Idle Valve Cleaning

[wan8dan]

I have ES300-96'. I thoroughly cleaned the idle air control valve and air intake
throttle, idle problem gone, but 2k miles later, low-to-no idle problem
re-surfaced when I start the engine. What else could cause it that I haven't
looked at?

Thanks

Simon

[wan8dan]

96 Lexus ES300
sometimes (especially when car left un-driven more than two days) get low idle
speed (less than 100 rpm) at cold engine start, have to step on gas pedal
slightly to keep it running. But a minute or so, idle goes back to normal.
Sometimes I also get high idle speed at cold start(ie: more than 1500 rpm).
I've cleaned intake throttle, idle air control valve, and MAF sensor about 9k
miles ago, but problem still persisted. Not sure if this is indication that
idle air control valve or throttle position sensor is going bad. Any advice
would be appreciated.