I made my '94 TPS Sensor adjustable...

[jmoore16]

After having rolling idle, tip-in stall and hot restart issues, I decided to check my TPS voltage (I have a bunch more experience with 89-93 Mustangs as you will find out...). 1.36 volts.

I know that my '91 needed .950 to .999 volts so I took off my Idle Air Bypass valve off to adjust the TPS.

Can't adjust the TPS on a '94-'95. Convinced this was my issue, I drilled out the sleeves to give me some slop in the holes so I can rotate the sensor. This eventually worked and I set .98 volts.

The car seems to run better with no stalling and approx 50 rpm roll for about 20 seconds instead of 250 rpm all the time. The car is also easier to drive away from a stop light.

Why is the TPS signal non-adjustable? Did I do something wrong that I don't know about yet???

 

[4Jenna]

I did the same thing (drill out) and set mine to .98, sadly these cars put it back to where they want it as soon as you start it..lol
They aren't adjustable, even with the drilled out holes

 

[jmoore16]

?????

How can the computer change the TPS reading? The only way that I know of is to change the input voltage. Mine still reads .98 volts.

I'm confused (Not hard to do - use small words and big pictures )

 

[Cyiberwulf]

Yeah, could you explain this in more detail? I'm thinking if this will help my GT and an easy fix, I'll 'try' this as I'm good with electronics...

 

[jmoore16]

Cyiberwulf - Do you want me to explain what I did or how the computer resets itself?

 

[Cyiberwulf]

Explain what you did as far as the TPS goes. Where to check the voltage, what to drill out, etc..

 

[jmoore16]

How to set TPS Voltage...

I first checked the voltage by running a safety pin through the center wire of the three pin connector running into the TP sensor. Make sure the pin is not grounded to the intake or anything else...

With the engine at idle, my voltage was 1.36 volts. With all my reading this weekend, an 89-93 car wants .95 to .99 volts and you get this by rotating the sensor. To rotate the sensor, you first have to remove the Idle Air Bypass which allows you to remove the two phillips screws that hold on the TP sensor to the side of the throttle shaft and housing. To get adjustment, you need to drill out the metal sleeves surrounding the two phillips screws. This gives you enough slop in the holes to rotate the sensor until you get less than 1.0 volts. To decrease the voltage, you will need to rotate the sensor counter-clockwise (connector will rotate up and away from the injector wires - added bonus) if you are looking at the sensor from the left front headlight.

Warning - the metal sleeves provided clamp load to hold the sensor in. Without the metal, you have to crush the plastic a little but it holds tight. Don't know for how long but it works so far and I have got the engine really hot...

I was able to get down to .96 volts and the car runs really well. The RPM hunting at idle has decreased dramatically and it runs much better at light throttle.

Make sense?

 

[Cyiberwulf]

With all my reading this weekend, an 89-93 car wants .95 to .99 volts and you get this by rotating the sensor.

Does this work for 95 as well? Just asking. Other than that, I think I can do this.. Thank you...

 

[Cyiberwulf]

Wohoo ... Mine's setting at 0.90v at idle I guess that's good as I didn't need to rotate it at all....

 

[4Jenna]

I had a scan tool hooked up to mine that told me TPS voltage. I drilled the holes out to get it where I wanted it.
I started the car up and nothing changed with the idle etc...Checked the TPS voltage and it was high again..all by itself. Did it 3 times and everytime it re-set itself.

I searched all over the forums and alot of guys have the same prob, and I thought it was fact that the TPS reset itself...but somehow yours is working so it's possible. Wish mine woulda worked!
I run a Fox TB now, so these probs are old news for me.

Chris

 

[HISSIN50]

Chris, on the foxes, the TPS should not reset. there is a juice feed, ground and the return. the sensor is a mechanical rheostat. i wonder if the sensor could have slipped a little after you set it....

another aspect is that the puter should "zero" out the TPS reading whenever the car is started. so as long as its base reading is not absurd, there is not any gain to messing with it.

now we all know that there are many folks whom swear that the adjustment made a difference. knowing these cars, i dont know that it would not - they are finicky with the idle surging and such. i could probably let my cat lick the plenum and it could help.

im not trying to contradict anyone, but rather trying to supply info (Chris, i only mentioned you, because your line of thinking was on track - the setting does not matter, and in essence does reset, but no via the TPS sensor, rather the puter instead).

good luck to all.

 

[4Jenna]

Good info, but I thought we were talking about 94-95 TPS
I have no exp. with a Fox tps, but heard they hold.
MY 95 didn't.

 

[jmoore16]

Probably right....

Because I understand how the TP sensor works, I agree that it doesn't do anything but it does. I even did an A-B-A comparison meaning I reset the TP sensor back to 1.3 volts and all the idle hunting and poor driveability at tip-in came back. I then reset it and it runs fine.

Is it possible that there is a default high end voltage (1.2 V? 1.25 V?) that the ECU uses if the TP sensor is out of range (1.36 V)?

If this is the case, then the ECU thinks the throttle plate is always cracked open more than it is and may not enrichen the mixture enough at tip-in. Possible?

 

[gcomfx.com]

I tried to buy a new TPS sensor at O'Reilly's.... they found 4 or 5 in the computer for our cars???? They told me to bring in the old one and they will match it. Could we all be talking about different sensors maybe??

 

[jmoore16]

gcomfx...

I know that my aftermarket throttle body has a different sensor than a stock '91 or my current '94.

There must be at least three...

 

[4Jenna]

Hmmm could be it, I was using my stock tps. Just transfered it over to my 70mm

 

[jmoore16]

Disregard this thread...

Didn't work. Search for "straight intake MAF" for what finally worked.