Hi Art,

Just read your post and I guess you are right about what is considered a “hairs edge” to many people.

I will have to say, that when I’m taken literally, I can get taken out with the trash! (:)

The whole thing I was trying to instill was the fact to tell the ECU to advance into the next program appropriately.
One has to keep the idle speed being controlled on the IAC.
The throttle plate can easily raise idle speed due to the surface area of circumference space.
You don’t want the plate open Too much and then have the switch turn state as you will be running in a mixture deficit and have stalling or higher idling issues just from that.
Barely cracking the throttle open will rapidly allow enough an inrush of air flow to instantly change the vacuum in the manifold plenum.
One has to remember that it was under an ideal lean idle mixture of control, to control emissions, to the set mandates.
The idle rpms are watched closely to reduce fuel consumption for the ratings system. Finally putting money into the high number of gears in the transmission instead of tricks.
Now they are going as far as disabling various cylinders or the whole engine.
Now that’s got to be a headache, maintenance wise, in short order.
With new cars you get ponder the difference between a maintenance gouge or being gorged up by the blue book resale depreciation!

The ECU program will be raising the injector mixture on the TPS command Long before the O2 Sensor responds. The AMM is oblivious to the oncoming change as well.

For my cars I admit I do stress on that a wee bit. It’s better than emitting! (:)
On some models this shift in program brings on the EGR function at some point? I think it does this in later RPM’s or at a road speed, so it affects the plenum less.
A sticking EGR, either opening or closing off completely can cause a drivability or CEL issue.

The East coast cars have less of those running around but we get to have less cars with rust issues.
Since you have more green trees and bushes, you have more “air cleaners” standing or lying around!
It must work because, at my Northern ocean home, my used cars are exempt from smog certification excepted when first purchased. Several counties are blessed that way luckily.
I stress on myself again to keep a car tuned up despite this.
It’s easier on starters and the fuel wallet. California fuel runs about a dollar or more a gallon, than the East Coast side, due to the taxation straw sucking in there!
My small California Northern community pays even more!
It’s like what Hawaii pays, due to supposedly mountainous roads and being small. It drops back $.50 within in California a 150 miles away, but Hawaii is 2,000 miles away over the ocean. Go figure as I do distributor greed.
I fill up in Oregon when ever I can. Thank heavens for interstate commerce laws.

Anyway Art, you are right on, as usual!
Good to see your hanging out and being a watchdog for us!

Phil