Howdy.
99 5vz (into a 95 body) Manual trans.

Really appreciate replies.
Background. Smashed 99 4runner, purchased, rebuilt 5vz, transplanted into a 95. Not certain it ran at all when bought.
Slow slow slow process. Started after about 5 cranks (when finally supplied with fuel). Had high idle. 2600 or so. Couple of months ago, forget all what I did. Anyway, pulled IAC back off again, examined magnet end and put back together. So, 3rd time to run: started, still high, got to oper temp (190 ish), was ambiguous with pedal/cable(?), or vacuum leak, or what. but about 11-1200 this time at warm. Weary of running too much, because it's still new, and need to accel/decel to break in off course. So it was idling at 1100, and for some reason I reached over, pulled the TPS off. Boom. Down to about 500. Think it actually died, too, on second try.
So good news, think I had got the IAC corrected, and obv no vacuum leaks. The ohms on the TPS are pretty linear that I can see. BTW, its about 570 ish (maybe to 620) up to 2.7K ohms.

Son--in-law loaned me a scanner. It says TPS is at 12.

Today I rigged up a test circuit so I can measure stuff. Blurry pic attached.
Get a 5.1V at pin 2 (VC). Good ground pin 3 (E2). Disconnected throttle cable, hand turned plate to watch V. Starts at 0.625V (12.5% per snapon) and up to 3.77V at wide open. Thats about a one second action each way. The V on the ol Fluke was pretty smooth and gradual from what I could see.

Attached is a photo of the TPS reading. Holy mayan temple batman. Talk about stepped response. Full is 75%-ish. But manual says thats fine. (Okay by me i guess).
But that looks like about an 8 bit resolution. 5 steps up, and 7 or 8 back down. THAT doesn't seem right. Remember the meter for sure did not display, whats that, 1/2V or so increments?
Obv, the ecm will do an analog to digital conversion, but that seems extreme. And that would also seem to mean you could only choose 'preset' rpms as you're driving.

So if the TPS 'passes' the service manual for specs, and also with a volt meter. Right?
Or does that indicate my ECM is flawed?
WIthout having actually driven it, the throttle also seems to be jumpy. But the cable is not stiff.

Thanks in advance.

 

Being a bit of a midwit or less, it occurs to me I need a comparison. Dropped by local dealer, asked Service Super. They said I'd have to bring it in so they can hook it up to their stuff and look at pico codes or whatever.

So, I said to myself "Self," said I. "You need to hook up a scanner to another similar and look at that wave form." Easy. Non-intrusive. Would point me in right direction. Find another or have this ECM rebuilt.

Thoughts anyone? Buehler?

 

The ECU isn't using the TPS for that purpose though. The engine output is governed by the throttle itself limiting the air going in the engine, and the AMM/MAF measures how much is going in and uses that to add the right amount of gas.

The TPS is mostly used to see if you're flooring the accelerator quickly (might need to do some acceleration enrichment), feeding a load signal to the trans ( if it's an auto trans, for wear/tear and MPG reasons, the trans doesn't pump full pressure all the time), and the ignition (some transitory timing retard).

Generally speaking, you could unplug it and the engine would run fine, mostly just a bit of a lean stumble as you put your foot down.

In some (100% aftermarket, performance 'racecar') situations if the engine doesn't make a decent manifold pressure signal (like individual throttle bodies) and they don't want to run the intake through a restrictive MAF, they might use 'alpha-N' mapping, which does map the fuel volume based on the throttle position. But that's pretty crude. But if you were doing that, you'd want a smoother TPS for sure.

But it probably doesn't mater on a 4Runner.

 

Thanks Jomoka. Thats good to know.
Going to just give it a try when I get back home. Hopefully I didn't mess up the transmission on 'rebuild' so we can progress.

(Note to self: That's an adult beverage owed next summer if you all come back this way again.)