1999 Eldorado intermittent high idle problem

99 Caddy Eldorado, 4.6 liter engine.
Approx once every two weeks, idle sticks at 1700 RPM.
Car has new computer, new IAC valve, no PCM codes.
Data stream looks normal when acting up.  When acting up, we can lower idle with Thexton IAC tester, the Thexton IAC noid light remains lit, but does not blink.
Any suggestions would be greatly appreciated

quote:

ORIGINAL: daviddonovan4

99 Caddy Eldorado, 4.6 liter engine.
Approx once every two weeks, idle sticks at 1700 RPM.
Car has new computer, new IAC valve, no PCM codes.
Data stream looks normal when acting up.  When acting up, we can lower idle with Thexton IAC tester, the Thexton IAC noid light remains lit, but does not blink.
Any suggestions would be greatly appreciated

Did it start that before or after the new computer and valve?