1985 Fiero 2.5 / auto. had the car 6 years, all was well. lately, it (Only when the engine is not warmed up) I'm in Fla. The engine "at start" will Idle at 1500 until it runs for a few minutes. Never did that before ! Cannot find a vacuum leak, but I would think a "vacuum leak" would affect it if it was cold or warm. Any Ideas ?
runs fine, just has that 1 quirk. Thank you.

Sounds like it's doing what it's supposed to do. Don't see a problem there, the 2.5's are known for their high cold idle.

no big deal, but it was never like that for the past 6 years. now it seems even after it running for a few min, it' still idles at 1500-1800

Have you unplugged the battery recently?

[This message has been edited by cebix (edited 12-19-2017).]

yes, I took off the cables to clean the ends. why ?

When you disconnect the battery, the ECM reverts to a predriven set of variables. Examples: back up the IAC valve to a factory setting, Enrich fuel when cold to a factory setting.
As the car is driven and also as the car ages, the ECM "learns". After a while the ECM normally will only back the IAC as much as needed to bring the idle to prom/program settings for the signals that it senses. There are other little quirks it learns. MAP, coolant temp, air temp, throttle position signals are not normally exact as the programming expects them. The ECM "learns" the little differences and adjusts itself.
So lets say you have disconnected the battery and look with a scanner at IAC counts. At first when cold it may put it at position 45. It senses that it was too much. So the next time you turn the key on and it senses the same conditions, it might set it at 43.
There are other variables to this. Example: it may expect to see TPS voltage at throttle stop to be .45v, but it senses .47v. Or that air temp is at 45 degrees and coolant at 47. Until it learns, it doesn't know these are normal and because they are not out of range it doesn't fail them and set a code and bring up the light.
Unfortunately for me I have been using my car as a daily driver for the past 2 years/17,000 miles. Even though i am using a faster 1993 PCM with a 2005 3800 n/a, if I loose battery feed, it still takes several days to relearn to get it back to what it was before hand. In mine, this also involves shift points. To most it wouldn't be noticeable, but I am very familiar with my car and also work on cars for a living.
Be glad that it is not an 80s Ford, where you have to go through a idle learn procedure or a Chrysler where they would run like crap until they relearned. On the older Fords, would have them have me convinced they learned idle, only to have them stall when coming to a stop if the A/C was on. The older Fords even used an "Ecell". A battery in the MCU/pre ECC4, that slowly depletes to simulate engine aging. Those were early computer controls and have gotten much better since than.

Very simple
disconnect battery or pull Reset connector will clear all "learn data" in ECM Memory.
That will force ECM reset IAC to find IAC 0 steps/position.
Until ECM does so... will force idle high because ECM has to guess where IAC is so goes only by RPM.

ECM will always reset IAC after starting when driving above ~35mph to check 0 steps.
Some will reset IAC when you hold the gas above ~2000RPM for 30sec to 1 minute but many ignore you. (87 and up DIS Dukes will but others may not.)

ECM will cause high idle when ECT reads too cold. In FL may happen but rarely. Drive north a state or two and is more common.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

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all better. thanks