Throttle cable shouldnt be under pressure, just loosen it enough to have just a bit slack (very little)
Now, this is a typical FIAV probelm. The lower part of the TB has two parts. One is the idle control that lets or stops air. The ECU regulates the idle motor so the engine keeps steady RPMs ( usually same as the base idle setting when engine is warm). The second part of the lower TB is the FIAV or choke. Theres water/coolant circulating around it and when its cold it raises the RPMs (usually in the morning), when the coolant gets warm the valve closes and the idle control takes over. When that valve gets dirty from residue in coolant system, bypass air from the valve cover that goes straight to the intake, contamination from the EGR...you name it...the valve gets stuck and usually lets some amount of air thru. Now why the idle is looping. Assuming that the closed throttle position switch is adjusted correctly( its built in the TPS). When that switch is closed it signals the ECu and the ECu cuts fuel to the injectors. With this said by factory setting with throttle switch closed the ECu hits fuel cut at 1200 rpms. So you have more air coming into the intake manifold the ECu sees it and tries to add more fuel, but it also sees that the throttle is closed and when it reaches 1200 rpms it hits fuel cut. The fuel is now less the rpms go down, the idle control catches it and then stabilizes it, but there FIAV valve is still leaking air that is registered by the ECU, it adds fuel the rpms go up, it hits fuel cut again and so on and so on........it loops all the time.
How to fix it. i personally used ful FIAV and ISC block off plate. Its a pain in the ass in the morning but I got used to it. There are also partial block off plates that eliminate the FIAV only - they are better for cold mornings. or you can try fixing it by cleaning inside the FIAV where the spring is or get a newer TB from 97 Hyundai Sonata. Most of the time they are in excellent shape, they are still 60mm and they are p'n'p
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