Bad TPS???

[MKIIBeater]

Well further testing shows that the TPS is cosntatntly putting out 5 volts. I do not understand why but I just assume its broken. At leist I hope. Im hoping thats its not doing that because of some type of constant ground somewhere or something. Im going to try and replace it and if that doesnt work then Ill now I have to chase some damn wires down. Thanks much...

PS- I wonder what this is doing for my fuel trims...consdiering the EFI runs the injectors and timing according to TPS, and the AFM. Although the AFM is functioning fine I wonder if the TPS is making things screwy. If anyone knows of anythign that this might be please chime in. THanks,


Austin

[MKIIBeater]

anyone =)

[Dave A.]

What terminals are you measuring on the TPS? How did you have your meter connected?

[MKIIBeater]

I just got a voltmeter and meausred the black wire from teh back of the connector while it was still hooked up. It showed constant 5 volts, so then I measure the others and got nothing. This was while fluctuating the throttle on all three with the car on and with the car off to make sure...

[MKIIBeater]

:lol:

[Dave A.]

What year is your MKII? Auto or manual trans.? The variable resistance type TPS was only used in 85 and 86. The others use the switch type TPS but there's a different one for the auto and manual trans.. The 85 & 86 use the same variable resistance type (round shaped) TPS for both transmissions.

[MKIIBeater]

I dotn have the round one, i have th erectangle one. Mine is a 84 p type Manual ofcourse... thanks

[Voyn238]

Sounds like you were testing the 5V constant source for the TPS. The square style ones do not output a varying voltage, they merely show continuity between various pins at certain points in the movement range. The TSRM or the Haynes manual should have good testing procedure.

[CRF_Rider]

Hmmmm. That could be a problem with the 82-84 supras. Specifically setting the hi/lo throttle points. If that were the case you would probably have to ignore the hi/lo throttle setting and have the same ammount of correction for both on the SAFC.

Anyone else have input on this?

[Voyn238]

>>
Hmmmm. That could be a problem with the 82-84 supras. Specifically setting the hi/lo throttle points. If that were the case you would probably have to ignore the hi/lo throttle setting and have the same ammount of correction for both on the SAFC.

Anyone else have input on this?
>>

The SAFC needs to see a voltage signal on one wire, and on the square TPS's, the continuity appears between different pins at different throttle conditions. This is why the SAFC won't work with earlier model Supras.

[CRF_Rider]

I will add this info to my post in the GTE forum.

[MKIIBeater]

Well this fuggin sucks... Is tehre a way I can convert to a 85 TPS? Anyone =)

Austin

[MKIIBeater]

Does anyone know where I could get in contact with someone who has an sfc on an pre 85's?

[CRF_Rider]

Well, you can just ignore the hi/low setting and set both the low and high throttle settings to the same ammount of correction. You might be able to set the AFM so that it it right on down low and have the SAFC do corrections starting at 3000rpms. You *should* be able to work something out between the RRFPR, AFM and SAFC. Problem is if you cant you are out the cost of the dyno.

I think if you swapped the TPS you would probably have to the the ECU also (as well as all the related electronics).

You may look at trying differnt throttle types (the arrow thingie). Maybe they have one compatable with your TPS? I will read the manual tomorrow.

[MKIIBeater]

No well you can just ignore the hi and lo. If I did and tried to tune on high it would give me the same corrections all the time and I obvioulsy would want it a little leaner on the lower throttle points...

Id be willing to bet the 85+ TPS have something to do with the knock sensor to. I do not know what to do right now with this, cause Id really like to be able to use the afc. I just do not understand why the sensor would be putting out a constant voltage like that. i tested all 3 wires in all positions and the 2 put out constant 5 volts where the other is prolly a ground of some sort. I still havent changed the TPS cause I figured if it runs fine and there are no CEL's then its prolly just the way it is. Do you think I shoudl bother spending the money to buy another TPS and see if its just mine? Or shoudl I sell the afc-2 and try and get something else to work for fuel adjustment? What else could I use, is there any other way to help tune like the afc can for our cars?


Austin

[MKIIBeater]

8)

[cheappower82]

Looking at my Toyota 5M-GE/6M-GE engine repair manual, I noticed the voltages are as followed:

up to Aug. '85 -
Throttle valve open: 4-6V; (IDL - E1)
Throttle valve fully closed: 4-6V; (Psw - E1)

Australian vehicles and 6M-GE from Sept. '85 -
Throttle valve open: 4-6V; (IDL - E1)
Throttle valve fully closed: .1-1.0V; (VTA - E2)
Throttle valve fully open: 4-5V; (VTA - E2)

These are voltages at ECU wiring connectors

Not sure if this applies to our case, but it does show significant differences that will affect the S-AFC. The S-AFCII manual has 3 TPS settings; none of which applies to the 3-wire sensor :bad-word:

[MKIIBeater]

Well i sont know what you mean about the 3 wire o2...that doesnt have anything to do with it. What I mean is that since the TPS at the ecu shows a constant of 4-6 (anything over 4 will read 100% to the afc) its not fully functional with our cars.

The reason being, is that since the afc has a high and a low setting feature you are normally allowed to control each according to TPS and TPS only. If the afc is always seeing 100% then the only thing we can tune for is high throttle. if you tune anything low throttle it will be disregarded sicne its always 100% and the low throttle maximum NE point is like 49% (signal from the tps) then its impossible.

However I was thinking that since we can screw around with the AFM's, that we could just adjust the afm leaner so it idles and does ok at low throttle, but during high throttle we can adjust the afc and it wil work, because we are always seeing 100% which is ok since the high throttle NE point minimum is like 50 or 60% or something and if it sees 100% it will adjust accordingly. I figure this is ok since Mark said that his idle and everything is ok with just the AFM adjusted as well as a few other MKII guys that dont even have an afc. So the advantage that we will have is we can lean it out a bunch with the AFM and then just ue th eafc to either richen or lean out a few spots where ever as long as its full throttle. So Im not all that upset anymore knowing that I will still be able to control at leist the important (full throttle) side of the tuning....

Im getting real close to finishing up my car. I will probably be done as soon as I get the rest of teh stuff from good ol' Aaron Garney. :evil:

[cheappower82]

Well i sont know what you mean about the 3 wire o2...that doesnt have anything to do with it.

Three wire TPS.....I have the same rectangle TPS

[MKIIBeater]

oh ok...no it doesnt affect us. You gotta be using it as a 6 cyl progressive throttle or else the setting wont work. There is only that one that works for us and it doesnt even work for 82-84 :cry:

[cheappower82]

Well if you still want to keep the S-AFCII, the hardest things to come by is the harness and the ECU ('85).

The throttlebody and TPS that came with my 6M-GE will work. So if you can locate the '85 harness and ECU, I'm sure that someone will sell you their 6M TB and TPS cheap (I may have extras laying around in storage).

[SlimFastSupra]

if you have an on/off type of TPS, you can add a MAP sensor from just about any car and use the vac to zero reading as the TPS input.. this way you can have varying conditions instead of off/on.

[SonyPete]

How similiar is the MAP readings compared to the TPS readings. Is it close enough, to use to tune easily?

Also I have an 83' Celica with the old school analog ecu system from what I understand. It is a really simple ECU, but I just wanted to make sure the SAFC II would still work with it. Since the ecu still tells the injectors how much and when to run. Would the SAFC II still work for me?

[SonyPete]

Any clues or ideas guys :lol:

Ohh yea how would you get the MAP sensor to work with boost pressure, read a little about probs and how to get it to work but still not sure. ANy help is appreciated :)

[jeremyisme]

I am trying to get my head around this TPS problem for the SAFC, is the main problem for the older ones, 82's, 83's that the voltage is too high off the TPS?
Couldn't you just make a voltage divider to drop the voltage into a range that the SAFC understands? As the voltage still varies right?

[cheappower82]

if you have an on/off type of TPS, you can add a MAP sensor from just about any car and use the vac to zero reading as the TPS input.. this way you can have varying conditions instead of off/on.

What he means about the on/off TPS is this: 85 and newer uses a variable voltage (true throttle position) tensiometer type TPS. As you depress the gas pedal, the sensor sends a different voltage per position (prorated). Some TPS's go from low to high voltage (0-5V), and some decrease with TP (5-0V).

The 84 and older (square TPS) act as an on/off switch. As the pedal is depressed, the TPS goes from no voltage to max (usually 5V).

That's the way it was explained to me.