SN95 Tps issues

Decostercl02 · Sep 15, 2022

I have a 95 gt. I added a 75 mm throttle body with a compatible air intake. It ran fine for about 100 feet till it started a high idle (2grand). The engine would stay at the rpm and speed that i left it at until I either revved it again or shifted. My tps will not stay at the voltage I set it to. So I replaced it and I'm still having the same problem. It feels like the throttle is getting stuck but only if the tps is plugged in. It runs decent if it's unplugged.if plugged in it won't start or idles high and the above problems persist. Any advice would be greatly appreciated. Local mechanic won't work on it due to being aftermarket parts. So yall are my only hope. Thank you.

Mustang5L5 · Sep 15, 2022

What voltage fluctuation are you seeing?

The TPS doesn’t need to stay at any preset value. While I don’t know the range on the SN95 cars, the fox cars use 0.5-1.25v as an acceptable voltage at idle.

The way it works is when you start the car the ECU looks at idle voltage at startup and assigns that a variable to identify idle. Whether it’s 0.85v or 1.1v makes no difference.

Generally if you are outside of the acceptable range you generate a code within the ECU.

Clarifying what you are seeing would help. Are you setting it to 1V and seeing it rise to 2V? Or are you seeing small swings in the 0.1-0.2V range. Generally as wiring heats up, resistance increases so you will see small fluctuations.

Decostercl02 · Sep 15, 2022

Okay that makes a lot of sense. So what do think is causing the throttle to get stuck open and Idle high. It only gets "stuck"/ high idle while the tps is plugged in.

Decostercl02 · Sep 15, 2022

Mustang5L5 said:
What voltage fluctuation are you seeing?

The TPS doesn’t need to stay at any preset value. While I don’t know the range on the SN95 cars, the fox cars use 0.5-1.25v as an acceptable voltage at idle.

The way it works is when you start the car the ECU looks at idle voltage at startup and assigns that a variable to identify idle. Whether it’s 0.85v or 1.1v makes no difference.

Generally if you are outside of the acceptable range you generate a code within the ECU.

Clarifying what you are seeing would help. Are you setting it to 1V and seeing it rise to 2V? Or are you seeing small swings in the 0.1-0.2V range. Generally as wiring heats up, resistance increases so you will see small fluctuations.

Also yes I'm setting it around there and jumping around. But after your explanation it makes sense that the sensor would fluctuate.

General karthief · Sep 15, 2022

The tps and the new throttle body are not jiving, put the original throttle body back on and see if it goes back to normal.

Decostercl02 · Sep 15, 2022

General karthief said:
The tps and the new throttle body are not jiving, put the original throttle body back on and see if it goes back to normal.

I was thinking about doing that but really didn't want to.

Mustang5L5 · Sep 15, 2022

Decostercl02 said:
Also yes I'm setting it around there and jumping around. But after your explanation it makes sense that the sensor would fluctuate.

Check your 5volt reference voltage. Make sure there aren’t significant swings going on there which would be a sign you have an issue with the 5v voltage regulator in the ECU

Decostercl02 · Sep 15, 2022

Mustang5L5 said:
Check your 5volt reference voltage. Make sure there aren’t significant swings going on there which would be a sign you have an issue with the 5v voltage regulator in the ECU

How would I check that?

Mustang5L5 · Sep 15, 2022

Decostercl02 said:
How would I check that?

There are three wires on the TPS sensor. A 5v signal reference, a signal return, and a sensor ground.

I don’t know the wire colors, but black is typically ground. Unplug the sensor and probe the wires with your multimeter until you find the right pair that gives you a constant 5 volts. That’s your sensor reference voltage

Decostercl02 · Sep 15, 2022

Mustang5L5 said:
There are three wires on the TPS sensor. A 5v signal reference, a signal return, and a sensor ground.

I don’t know the wire colors, but black is typically ground. Unplug the sensor and probe the wires with your multimeter until you find the right pair that gives you a constant 5 volts. That’s your sensor reference voltage

Okay thank you for your help I'll try that tomorrow thank you

General karthief · Sep 15, 2022

2.) Defective TPS - replace TPS. An idle that sticks high and won't come down unless you turn the key off & restart the engine is a sign of a bad TPS or dirty TPS electrical connections. The Idle will often start up at normal RPMs and then slowly increase in RPMs as you drive.

Disconnect and clean the TPS electrical connector using a jeweler's screwdriver to scrape the outside of the male pins and inside of the female pins. Use some WD40 to wash things down after you finish scraping. Check and clean the white 10 pin electrical connector pins (see item #6). Clean pins 1,2, & 5 since they are all TPS related.

Setting the TPS: you'll need a good Digital Voltmeter (DVM) to do the job. Set the TPS voltage at .5- 1.1 range. Because of the variables involved with the tolerances of both computer and DVM, I would shoot for somewhere between .6 and 1.0 volts. Unless you have a Fluke or other high grade DVM, the second digit past the decimal point on cheap DVM’s is probably fantasy.

Since the computer zeros out the TPS voltage every time it powers up, playing with the settings isn't an effective aid to performance or drivability. The main purpose of checking the TPS is to make sure it isn't way out of range and causing problems.

The Orange/White wire is the VREF 5 volts from the computer. You use the Dark Green/Lt green wire (TPS signal) and the Black/White wire (TPS ground) to set the TPS. Use a pair of safety pins to probe the TPS connector from the rear of the connector. You may find it a little difficult to make a good connection, but keep trying. Put the safety pins in the Dark Green/Lt green wire and Black/White wire. Make sure the ignition switch is in the Run position but the engine isn't running.
Thanks to jrichker and others for this snippet from the 'surging idle checklist '

revhead347 · Sep 17, 2022

Almost every aftermarket throttle body has a idle bypass adjustment, which the factory throttle body does not. It's a little screw somewhere on the throttle body that adjusts the amount of air that is allowed to bypass the throttle blade. This is used to take load off of the Idle air controller for heavily modified engines. Screw that completely closed and see what happens.

Kurt

CAMTWO1070 · Nov 22, 2022

Any headway to the problem?

From what you describe would be classified by me as possible installers error plus too big of a TB unfortunately as when you change the throttlebody to a bigger size you must also put the correct corresponding sized EGR plate to match the larger TB. You should of actually went with a 70mm TB too...

Usually when I make a change and it becomes unfavorable I put the old part back in to rule out the part that was installed was the problem or the way it was installed...

And over the years with all the TB's Ive bought they usually show the recommended parts that you must buy extra to complete the install which they leave out in their speil when bragging about what it will do for your vehicle....It should be This TB along with matching Adapter plate for $79.95 plus the EGR spacer sold seperately for $150.00 will yield extra torque and revs to your Mustang;- but they dont and hide the facts about the extra adapter and spacer in the instructions.....LOL

Plus in the notes states that the intake must be port matched when using a 75mm TB and should be used in higher HP applications..too..

SN95 Tps issues

Decostercl02

New Member

Mustang5L5

That is…until I whipped out my Bissell

Decostercl02

New Member

Decostercl02

New Member

General karthief

wonder how much it would cost to ship you a pair

Decostercl02

New Member

Mustang5L5

That is…until I whipped out my Bissell

Decostercl02

New Member

Mustang5L5

That is…until I whipped out my Bissell

Decostercl02

New Member

General karthief

wonder how much it would cost to ship you a pair

revhead347

Apparently my ex-husband made that mistake.

CAMTWO1070

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