extreme high idle

[quote:3d84beadb0="bnz90"]1993 ford tempo 2.3L 109,000 miles
One day started engine and idles at 3000 rpm. No check engine light, no codes stored, scanner shows normal values. Loud humming noise from intake tube between tb and maf. Replaced iac and engine now only idles down when snapping throttle and humming noise is gone. Turn car off and restart and engine idles at 3000 rpm again. What am i missing?
I reinstalled old iac and humming noise returned. Replaced maf along with new and old iac and no change in idle.
Checked engine temp sensor. Its good. What else am i missing?
Thanks,
Brian[/quote:3d84beadb0]

Try checking the throttle body plate might be all coked-up and not fully closing and computer throwing fuel at it because of the signal from the TPS. Could also be vacuum leak.

1994 Mercury Topaz 2.3L approx. 100,000 miles

Brian, I have almost the same problem with this vehicle. idles between 22-28 hundred rpm. Replace all intake manifold gaskets and obviously bad vacuum hoses. IAC replaced with bone yard variety but functional. Throttle body was extremely dirty exspecially the EGR port, which was completely plugged. Still has same problem. Looking into the EGR position sensor. Approx. $55 for new. Don't know how to verify if bad or not. Was suspecting Engine temp. sensor. No engine lights or codes that I can decipher. Will look into removing all vacuum lines like brake booster and hvac lines to see if there is a potential vacuum leak.