milano maroon

iTrader: (1)

I just wanted to pick everyone brains on this subject. I have read a lot of archived posts which talk about the procedures to follow when setting the TPS. While they all outline the steps to follow to get the two ranges within specification only a couple of them talk about the initial starting point for the idle adjustment. So I was hoping someone could shed some light on what happens when the TPS is out of adjustment one way or another.

Right now my car (HBP) idles fairly well and evenly at less than 1000 rpm. I believe I owe a lot of this to a working ISC (and a lot of help from Ray and Chuck). It is my opinion that with a working ISC you have some variability with where you set the Idle Adjustment Screw (IAS) on the front of the throttle body. I have been able to maintain my idle speed by incrementally screwing the IAS in almost 2 turns (I did this to try to fix a stalling problem when I would come to a stop sign). I have to assume that the ISC which is being controlled by the PowerFC is compensating for this additional air at idle.

But this is also my starting point when I adjusted the TPS. So I am curious what I have really done? If I am within the low range spec. but my throttle blades are open more than the ECU thinks they are how does that affect drive-ability? The stalling I was experiencing when coming to a stop sign is diminished. But what are the consequences as I open the throttle? It would seem that I am putting more air through than the ECU thinks I am. Does this affect tip in? Perhaps all of this can be compensated for by increasing fuel at accelerator movement or increasing fuel in individual cells but I would rather set things up correctly at the start and tune from there.

So here is, finally, my question(s):

Where do I set the primary throttle blades prior to setting the TPS?

Just closed?

Or at the factory paint mark which I think ends up being 1 to 2 turns open from completely closed?

Can anyone guess what is happening (in terms of drive-ability) when the throttle position is being incorrectly reported to the ECU?

Thanks for any help with these questions,

Jeff

catch-22

iTrader: (2)

this should help

https://www.rx7club.com/showthread.p...%2Btps+%2Bbuck

milano maroon

iTrader: (1)

thank you for the reply. i read that post, it and one by howard coleman are the only ones i have found which discuss initial throttle body blade settings.

i am inclined to reset my tps per this post but was curious though what everyone else was doing and what the effects were on drive-ability.

existanzrx7

iTrader: (8)

Here is how I fixed mine.

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/fixed-my-idle-problems-backfiring-bucking-more-170731/

arghx

iTrader: (3)

In my experience the Power FC is a lot less picky than factory Mazda computers. Series 4 FC's run especially bad when the TPS is out of adjustment. I think the factory ECU uses more complicated emissions control logic and that's one of the reasons why it's more prone to being messed up by a bad TPS signal.

With a Power FC I usually adjust the TB first to get the idle decent, then set the TPS after that so it's in range. I've seen Rx-7's with TPS signals slightly out of adjustment still run well. The PFC isn't even as picky as you would think. For example, you can run a narrow range signal VTA2 to the VTA1 wire. Both VTA1 and VTA2 have same voltage, coming from narrow range TPS signal. In fact, that's what I do on series 4 FC's because they don't even have a full range TPs. The car will still run fine after some adjustments.

You're welcome to play with it and see what happens, but I'm not sure how much of an improvement you will see if the car already drives decently. You may spend a couple hours messing with it and end up back where you started.

gracer7-rx7

iTrader: (16)

Out of adjustment TB mechanical settings will cause an unexpected amount of air (greater or less than expected) for a given TPS setting. You will typically see the affect of this with small throttle movements that cause bucking or when returning to idle - particularly when the low movement setting is out of spec


You mentioned Chuck. If you have his notes, go through his steps for TB adjustment. It is the best step by step guide I have seen. I don't remember the details with regards to the paint marks and such so I won't comment on that.