First off let me say that my last 4 trucks were diesel and ALL of my 4x4's have been the same.

Sometimes my 22re in my 86 SR5 will idle down, or up depending on how it feels, and it will even do it while I'm looking under the hood. What I don't understand is when it does it nothing moves under the hood. The throttle body valve flapper thing doesn't move, the throttle cable doesn't move.... nothing moves it just changes idle.

How in the heck does this happen? Is it one of those things like area 51 that just is?

I'm sorry for the odd question but when you go from a 1977 Scout with the IDI SD33 NA diesel in it everything else seems complicated.

 

Yes, it is just like area 51.

You have an electronically controlled system as many of us do. Consider yourself part of our cosmic family. With our vehicles having computers, they have minds of there own. That is to say, we are not in control. THEY are! They, meaning those above who idle in the cosmos upon the Mothership. When the time comes, we....those of us with our EFI's...and particularly Toyotas (I think there's approx. 144,000 of us) will be beamed up and the Earth will return to carbureted vehicles and suffer the fates that go with "lower" technology. It's sad, but worry not over your confusion. It is only a transitional process as our ECU's are daily adjusted to cosmic cycles in preparation for The Event.

All praise Toyota....Om Nah Ma Toyota!

 

That has to be one of the strangest answers ive ever read.

You might want to check the throttle position sensor, if its out of adjustment or going bad it can cause the problems your having.

 

Well, it was only a joke, guy. (Strange is very relative..... )

But, to actually answer the question....
The ECU reads voltage signals from the various sensors and switches of an electronic FI system. The TPS....as he suggested...is a good example. It senses the position of the throttle plate inside the throttle body through specific voltage and resistance ranges and adjusts the ignition and injector timing accordingly. If the TP is wide open, for example, the ECU advances the timing and increase fuel delivery to compensate. When the TP closed, the ECU detects the vehicle as idling and reduces both. Either way supposedly creating better performance and efficiency. It's not always the case.

Anyway, if the TPS is damaged or aged, those values that the ECU reads can be out of range....as in, not truly reflecting the condition.... and the ECU attempts to compensate by advancing/retarding the timing and fuel delivery. Sometimes it acts like a seesaw and the idle...for example...will fluctuate.

So, while nothing mechanical may be moving, voltage is. Hope that makes sense.