Steve, you do realize that thread is almost 4 years old and the OP was banned, right?

Thank you for the tip, Steve.

May be true for other brands in the GM line, but in 13 years of moderating this forum, i don't believe we've EVER had a single owner have to replace the throttle body on an S series to achieve a normal idle 850 ish on a M/T).

1st design ECTS failure and associated connector corrosion accounts for about 70% of everything that hoses the operation of the S series engine.
Front O2, dirty EGR, vacuum leaks (especially at #1 on 2nd and 3rd gen SOHCs -- the gasket gets partially sucked into the port and therefore unmetered air gets in and messes up the A/F ratio......) CKP (no signal = no spark + no fuel inj pulse = not gonna run.

My guess (since I never took one on this thread) is that

1)the ECTS was not a GM sourced ECTS. The BS ECTS in there was defective or failed. As they usually failed open, the V across it (0) is translated at the PCM as about -40. It never changes. Engine heats up. If cooling system is tight, temp usually stabilizes and you are fine until you get stuck in traffic and the coolant temp rises b c there is no air flow across the engine.

The aux cooling fan enable is triggered by the ECTS, which is always interpreted as-40 in this case. So the cooling fan never turns on and the engine overheats.

I don't know if his expansion reservoir was almost empty from overheating and him not refilling it or if the cooling system had a leak. I suspect both, actually.

Running with a SUPER RICH mixture meant for -40 degrees will jack up your idle into the 2K range (not uncommon).

I bet a simple throttle body cleaning would have been the first one the car ever had and would have allowed the plate to move freely to its intended destination, and the idle air passage would have been cleaned out to allow the proper amount of air to bypass at idle. As it was, that passage was probably restricted, not allowing enough air into the mix regardless of IAC operation. This, in turn, would force the engine to get the needed air from SOMEWHERE to satisfy the A/F ratio commanded in the fuel map for idle. That somewhere would be a vacuum leak, most likely at the intake manifold. If it was a metered air intake, the idle would be expected to go down; since it is unmetered the rpms go up since the air isn't accounted for in the A/F ratio to determine fuel requirements.

IIRC, the PCM will get the rpms as close to normal idle as it can by futzing w the air/fuel ratio, but will stop futzing when it determines no further improvement can be made.

Also the fact that the vehicle seemed to run smoothly otherwise removes a lot of things from the equation.

Throttle position sensor? Not really consistent with the ghetto cruise control he mentioned since it was not a constant FORCED rpm but more of a mutating one that slowly rose. Could have been checked with a DVM.

So in summary:
1) Dirty Throttle body and restricted idle air passage
2) Prob IAC from being gummed up
3) Non-GM sourced ECTS and almost certainly failed ECTS
4) Vac leak
5) Possible cooling system leak

I understand why the guy sold it for $500. It is a confusing mix of issues contributing to the observed behavior if you don't know Saturn S series engines.

Another useless forensic analysis completed that hopefully partially convinces Steve that the S series engines had some common issues of their own, but throttle body replacement was never necessary (in that I've not seen it recommended on this site, not that it is never the issue)

I'm sure there are cases where it is warranted, but, like S car PCMs, failures are few and far between.