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Well... i have had an issue with high idle for a while now. It revs high at start up and will stay around 2-3 grand until you restart it when its warm. The car will also drive itself at lower speeds due to the higher idle. I have a 2002 Buick Regal Ls. it has a new iac, i ran seafoam, got a new coolant temp sensor, made sure the throttle plate wasn't sticking, cleaned the coil packs, relatively new spark plugs and a few mods such as a zzp 1.0 pcm cold air intake, upgraded exhaust and aesthetics (unrelated). Anyways I've checked for vacuum leaks but couldn't find any so i am going to try a smoke tester as well. I'm hoping that someone can help. I wasn't able to find many answers online. Thanks in advance Josh
 

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Did the issue begin right after any of those mods? Or after any type of work done?
Was it gradual or did it one day just idle higher.
If you replaced the IAC and did not do a relearn that’s could be the whole issue.
It does require a capable scan tool to perform.
 

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Did the issue begin right after any of those mods? Or after any type of work done?
Was it gradual or did it one day just idle higher.
If you replaced the IAC and did not do a relearn that’s could be the whole issue.
It does require a capable scan tool to perform.
It did not no. I was doing work on one of the vaccine hoses and then it started but I checked for leaks and that wasn't the issue. It wasn't gradual either it was just an issue from the start. The scan tool is a great idea to try thanks.
 

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I would try doing the "hose stethoscope" check around the top of the engine, to possibly identify where a leak may be. The hose will isolate your ear to just hear where it's aimed, and you'll immediately notice any sucking noise increased if a vacuum hose or seal/gasket is the source. (can also be a good check/practice, regardless of if there's another issue)

The IAC shouldn't need to learn anything, as the PCM will regulate voltage to increase or decrease IAC setting based on idle conditions (I've traded out entire TB/TPS/IAC's between cars, and it's not been an issue). If it's commanding very high or low numbers, it's due to an alternate issue while it acts as the throttle blade trying to control RPM.
 

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Using a tech 2 scan tool there is 100% an IAC learn function.
I don’t argue it’s likely a vacuum leak, perhaps even a stuck PCV. But an IAC without a relearn in the older models can create issues. Once had a 2001 Lessbre and the the IAC was replaced, problem remained. Tried another warranty IAC and same result. Did it one more and it was still an issue. Did the learn and no probs anymore.
 

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I don't doubt there's a function, and it has a purpose, but with how many thousands of people have played musical sensors and throttle bodies/adapters with different IAC pathways, it would've been as readily known as the CASE learn if these things went awry regularly. Just as with a TPS, the IAC would have to be really out of whack to not register properly and require adjustment.

TL;DR - is it a thing? yep... how far down the troubleshooting list should it be? pretty far down, since there's gobs of simple high-percentage failure points that require much less to tackle (just my logic pattern for this stuff)
 

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Great idea with the hose stethoscope I haven't heard of anything like that. It has been resolved though. It was a small vacuum leak, but it was mainly the IAC getting stuck on the inside of the throttle body. Thanks for the help!
 

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Josh have you checked your bottom O-ring on the PCV valve? I replaced it with a viton Harbor Freight O-ring (the GM set is about $20-30) and lost a 200 rpm high idle. I know not much of a high idle but it prevented several of the engine monitors such as the egr from being checked. I did multiple smoke tests to find the vacuum leak and saw nothing because the leak is internal. Are you going to make your own smoke machine? Mine was made out of mostly disgards including a metal coffee can and a 5 gallon metal bucket. Anyone that has a metal coffee can or a metal bucket is fairly ancient (yours truly). As you have probably seen on youtube they are not that expensive to make. I don't see you have any computer error codes with this high idle. My second O-ring problem was the brake booster connection to the intake manifold. I crunched it when I installed the brake booster line after putting in a new plenum gasket. That was several hundred rpms that went away with that fix. What is/are your long term fuel trims?
 

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That sounded more like a "bull in a china store" style of install stories than anything else. :LOL:
 

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Hulk-smashing some o-rings is a matter of taking your time (I know that's not always easy to do, but slow can be faster, sometimes). I've also picked up that HF set, and carefully match any sizes/thicknesses, or else buy them elsewhere, as you mentioned..
 

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Hulk-smashing some o-rings is a matter of taking your time (I know that's not always easy to do, but slow can be faster, sometimes). I've also picked up that HF set, and carefully match any sizes/thicknesses, or else buy them elsewhere.
Interesting take with such great positivity. I changed the plenum gasket because it needed it. High rpms at idle. The booster o-ring did not come with the kit and looked fair. When I plugged the brake booster line felt like a nice easy fit (not forced) when connected to the plenum especially since I couldn't see it or could only apply limited force due to my short reach. I put a tiny bit of grease to make sure it stayed on and plugged it in. Didn't feel like the o-ring was offset but live and learn. Being 68 I don't have the strength I had 40 years ago. I plugged it in after cinching the plenum down in 3 stages with the inch pound torque wrench. The normal care one does when working with a plastic fixture. Never had any previous problems with o-rings or seals in my 30 years of farm mechanics, and working on cars. I would have thought my reckless repair would have impaired my fixing of labwashers (lab grade dishwashers that cost $20K), distilled water apparati, and autoclaves that sterilize media (at 1 atm) to test for bacteria and sterilize PPE. Tons of o-rings there. But then again I must have "Hulk smashed" them too. I hope one day I will be able to emulate your brilliance, perfection and the ability filter the most helpful salient issues combined with your tactful presentation to facilitate a car repair issue. Trying to put down someone trying to make a contribution is such a good trait in a moderator. Be sure to add a smiley face to a derogatory comment since it encourages people to make suggestions.

My point was using my newly made smoke machine (they are so handy to have around) made that find easy since the plenum is high up in the engine and smoke even in the tiniest of spots will come out. However, since the o-ring on the PCV valve is internal it is worth a look since a smoke machine will never find it.
Also Josh if you can get a cheap scanner with a long term fuel trim the immediacy of the change of said number validates your fix. My Ancel AD410 only cost $35 on sale.
 

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Nuance, humor, and sarcasm can be difficult to convey across the internet. There is no need to get defensive over my suggestion that care is a critical need for sealing pressurized items.

My daily job is in a CBRN laboratory, and sealing/pumping things down to 0.1 torr is a common requirement in some tasks.

It is not meant as negative commentary to investigate parts failure, human or component-based. Bringing levity to the conversation is how I acknowledge we're all prone to mistakes.
 
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