A friend (who generally knows his stuff) tells me that setting TPS idle voltage over 0.5V, even as high as 1V, at idle is now considered a "good" thing and will help with responsiveness. Of course every book I have says 0.5V, and I found nothing here about it, so I was wondering if anyone could explain why this would be good, or if this is not accurate...

Well, for that matter, how does the ECM "know" what voltage closed is anyway? 0.5V seems to be the target, but how close is "close"? I've modified the TPS to be adjustable, and set it anywhere from 0.43 up to 0.68 and it does not seem to matter.

If I remember correctly there was some talk a while ago about setting it for .61 or thereabouts for better response, but I tried that and it did nothing. I left it at the factory setting. I saw no truth to the fact that it was better.

I wouldn't set it anywhere but the stock setting. I believe that just let's it achieve its entire range of voltage motion. The computer should basically calibrate it every time you start the car I think it "zeroes" the TPS percentage. I couldn't imagine wanting anything besides spec setting.

A lot of Ford guys do that...

Here are some line of thoughts on it. By "Fooling" the ECM into thinking the TB is open more than it is, you may richen the mixture (same idea of an IAC relocation), as well as enter PE mode with less throttle opening.

Secondly, it ***Might*** increase responsiveness theoretically, because the ECM is fooled into thinking the TB is open further... I think that would be very hard to prove.

On the down side - none of these things make up for proper prom tuning. Also - later GM ECM's took the defualt "Ignition On Voltage" and made that the 0 setting for closed throttle. Not sure if they did that with TBI as well. Messing with the TPS will in result yeild nothing, because you haven't fooled the ecm of anything.

The less you lie to your ECM the better.

On the '8746 ECM, and probably the '8063 ECM, as the code reads the TPS it saves the lowest ever seen value. This lowest seen value is the starting point as 0% TPS. It is reset at each key-on, then recalibrated once the engine starts. It is ongoing as long as the engine is running.

So if the car is started with the foot on the pedal a little, once the pedal is lifted and the TPS volts drop, that is the new lowest TPS value.

This is a self calibrating feature and nullifies any attempt of gaining anything by setting the TPS voltage higher or lower.

Although, setting the TPS too high or too low will set a code.

RBob.

P.S. the ever popular '747 ECM does the same thing.

Thanks much, I figured it had to be something like that since the Truck (and whatever else) TBI TPS isn't even adjustable so at best it could only "somewhere near 0.5V" at idle. I guess this is a case where he just got some bad info...

Very interesting info RBob..TY!

I think after the CC carbs, all ecms/pcms began using that stratagy in one form or another.