What existed first?.... the chicken or the egg? ......
You are making conclusions based on a setup config that is not normal for the EEC (SPOUT removed = initial advance being checked or SPOUT circuit is open = failure code condition) OR.... did you know spark advance is RPM based (among other inputs).... not RPM control based on spark advance? .... which actually happens if the IAC is offline, within a working range....
Yes, I knew this.
BTW.... has it crossed your mind the possibility that when you didn't notice this rpm control detail, it may have been caused by a failure elsewhere, you weren't aware of (like a disconnected VSS)?
I'll never say that "something" is impossible but I've owned the car since 1991 and if I drove with a disconnected VSS, it connected itself after 17 years last fall. I've done all the work on this car so I know that no one else has tinkered with it. If the VSS is causing my idle speed to jump up when I depress the clutch pedal, what would be the results of me disconnecting it?
You have a computer with a program and preset working parameters, rpm control included and monitored. If you have such a setup with no rpm control failure codes showing (12 and/or 13 KOER).... the system is working within its designed threshold. Is the non presence of idle control failure codes a reason to fix an idle control problem
When my IAC wire is plugged in
, these are the codes that I get:
KOEO-----34 EVP voltage above closed
KOER-----34, 41 & 91 System reads lean passenger and driver's side
Cap, rotor, spark plugs and both O2s were changed out last fall after I started having the idle issues.
In addition to the very annoying increase in rpm when I depress the clutch, I also get high idle speeds of at least 850rpm and sometimes as much as 1000rpm while sitting at a red light. And to top it off, my gas mileage goes straight down the toilet. I lose about 3-4 mpg from the low 20's down to about 19 mpg.
The idle quality
(not speed), however, is perfect. Just like a brand new car. There are no symptoms of a vacuum leak; no stumbling, hesitation, roughness, etc. I'm not saying that there isn't a vacuum leak, I'm just saying there are absolutely no "engine running" symptoms of a leak.
I know that you're saying that this idle speed is "normal." I know that there is programming in the ECU that may result in some of what I'm seeing. Due to the internet limitations, you can't see or experience what I am. I know how the car behaved before and I know that something changed last fall. I have another EFI manual transmission car and while it is comparing apples to oranges, it doesn't do what my '91 GT is now doing.