2003 Buick lesabre very high idle

Buick lesabre 03 3.8l engine, idles at 2300 when it’s hot, cold start it idles just over 1000 rpm’s. Came from another shop where they replaced the throttle body, MAF/ IAC/ and TPS. No check engine light, no codes, fuel trims are normal, o2 sensors are working fine. TPS is a three wire, 5v ref is good, signal at idle is .438 and spec is .5 of a volt even when it’s idling high and the ground checked out fine. Check the IAC, not sure if I did it right or not,  it’s a 4 wire sensor, coil A+ coil A- and coil B+ coil B-. With a lab scope I connected one lead to coil A+ the other to coil B+ and my third lead to battery ground. Started the car and my square waves were glitching and dropping out on me. Both signals were adjusting from zero to charging voltage but again it wasn’t pretty. I did and IAC relearn on it and it dropped my idle down to 830-870 rpm’s. This was the best it’s idled. I rechecked my signals to the IAC and they seemed much cleaner, no glitching or dropping out. I allowed it to idle for almost 40 mins and it did great. I was almost ready to take it for a drive, I snapped the throttle on it and the idle dropped to 1000 rpm’s and with in a min it was back at 2300 rpm’s.. I wasn’t able to do a second relearn on it, all four of these wires go to the pcm, are there any other checks I could do? Anyone else have this issue? If I’m lacking information feel free to ask for, I’m kinda stuck and not sure where to go from here. Do these have common issues with the pcms? Is this a pcm issue? 

YOU MIGHT CHECK
1 CABLE BINDING
2 AC CLUCH WIRING ,TURN OFF AND ON FOR DIFF
3 STEERING PRESSURE SWT TURN STEERING R@L
4 INTAKE LEAKS OR WIRING TO ECM
5 GOOD LUCK

No vacuum/intake leaks, as I mentioned fuel trims were pretty normal. LTFT -5 to -7 and STFT was bouncing from 0-3 percent. At worst it was -7 percent which wouldn’t suggest a leak, the cables fine, no binding, as for the rest I did notice some of the circuits were shared but again, ref is steady, ground is steady and signals aren’t shared..

I was really hoping to get some help with this one… I came in early today, disconnected the battery to wipe out the pcm. Connected it back, went to idle air control relearn and relearned the idle air control valve. I was able to drop the idle down to 750-800 rpm’s. My tps % was at 0 and my IAC was at 40 counts and it ran fine until it got hot. I snapped the throttle a couple of times and my tps shot up to 20 percent, IAC went to 105 percent and rpm’s went up to 1400.. the hotter it gets the higher my percentages are climbing… is there another input that could be causing this that I’m missing? Any suggestions at all? New maf, new throttle body, new IAC and new TPS.. its cable driven tps and stepper type IAC…

when they replaced the throttle body did they replace IAC with it? if not that is what it is sounding like is the IAC is sticking otherwise a bad new part. If they have not replaced it I would be leaning that direction as well as cleaning out the bore the IAC sits in. Can you post the waveforms of the four leads for IAC please? 

Also did you do a throttle body relearn as well as an idle relearn? idle relearn will take a bit to do and sometimes will idle high and work its way down till complete or stumble a bit and then idle smooth. I also second the power steering pressure switch tests as that will increase engine speed while turning wheel but not to 2300 rpm usually it will increase from 650-700 to 900-950

also check purge solenoid and vent solenoid for correct function Purge valve for flow during non purge. this can cause higher idle as it can get fuel vapor as well if vent valve is stuck closed.

Years ago I had a similar situation with my 98 Chevy K1500 truck with the 5.7L. It idled very high even after driving it 30 miles. Turned out that my thermostat was bad and was not letting the engine to get up to normal operating temps. I had already replaced the IAC with no results. A new thermostat fixed the issue. The coolant temp sensor is also probably part of the system so you might check that as well.
In my case, I believe the PCM thought that the engine was cold all of the time like it was on a cold startup and wasn't letting the idle come down.  I also had no CEL.

UPDATE… So, I wasn’t expecting comments, so I went home and watched a few hours of section 20 (idle speed controls) functional testing part 1 and 2…. Every sensor was new on this car, IAC, tps, maf and throttle body.. I wasn’t worried too much about those particular parts or about carbon very much or. I was worried about circuit integrity. Or a possible pcm issue.. Danner did an amazing job of how to test the computer divers using an LED test light, cycle the key on and off, test light connected to ground on all four wires as well as 12 volt feed on all four wires, sensor unplugged. Every thing tested good there, no computer driver issues. I also lab scoped it and when one circuit was high the other was low, two key tests. I then took the IAC off (plugged in) used my thumb to check for in and out movement. It wasn’t as nice as his but I wanted to keep it simple. Parts are all new circuits look good, I’m assuming it needs to relearn and as I mentions before I did a relearn procedure.. well, turns out it wasn’t a relearn procedure as it stated (resets and relearns) it was simply giving me control of the idle. The relearn procedure was driving it… extendedly.. I put about 40 miles on it and it’s running great… I’m going to put another 10 to 15 before I release it but I feel really good about it. Hope this is helpful.

thanks for up date .. yes you should drive it .

Good to hear, hope it straightened right out after a good drive.