1993 Mustang Cobra TPS Issue

[Tbrake1978]

Hi Everyone.
I have a surging idle issue. Here is what I have done so far.

All vacuum lines are leak free
TPS is reading 4.95V (Tested with Green wire and Black KOEO) I have ohmed the wire (Black wire to Negative Battery post) .3 was the reading.
I loosened the 2 screws and no voltage adjusted what so ever

I have unplugged the TPS and it starts but still surges.

Any ideas? Bad TPS?

It will surge and then idle just fine and then randomly it will go into the surging again.

PLEASE HELP!!!!

 

[MG0h3]

Sure you’re on the right wire. Been awhile but if I recall it should have 3 wires.

Ground
5v ref
Signal.

Put your ground lead to ground; the actual sensor ground is best but any ground will suffice.

Probe each wire while sweeping the throttle blade.


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[MG0h3]

And a lot of times a surge is caused by high idle or vacuum leak and the IAC is chasing the high idle causing the surge.


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[Tbrake1978]

Sure you’re on the right wire. Been awhile but if I recall it should have 3 wires.

Ground
5v ref
Signal.

Put your ground lead to ground; the actual sensor ground is best but any ground will suffice.

Probe each wire while sweeping the throttle blade.


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I tried the battery ground,the sensor ground, and my ground strap. I'm tapping into the green wire.

As far as the vacuum leak goes I am not sure where it would be leaking. Checked all hoses.

 

[ashleyroachclip]

Have you checked the iac ?
Idle is controlled buy the computer, and iac .
Smoke test the vacuum system to find leaks .

 

[Tbrake1978]

Have you checked the iac ?
Idle is controlled buy the computer, and iac .
Smoke test the vacuum system to find leaks .

I unplugged the IAC and it will not start. My next step is to smoke test the system

 

[ashleyroachclip]

that says the iac is working .might clean it real good to make sure it is working efficiently.

 

[Tbrake1978]

Yep. I cleaned it. It wasnt that bad when I cleaned it. I have a dyno tune scheduled for this Thursday so hopefully they will be able to get it figured out. I just have to drive 44 miles to get it there and worried it might have issues with dying

 

[Tbrake1978]

Yep. I cleaned it. It wasnt that bad when I cleaned it. I have a dyno tune scheduled for this Thursday so hopefully they will be able to get it figured out. I just have to drive 44 miles to get it there and worried it might have issues with dying

 

[Tbrake1978]

Yep. I cleaned it. It wasnt that bad when I cleaned it. I have a dyno tune scheduled for this Thursday so hopefully they will be able to get it figured out. I just have to drive 44 miles to get it there and worried it might have issues with dying

Why am I only getting 4.95v? I should be getting something in between .70 and 1.0. What am I doing wrong?

KOEO red lead on green wire a
black lead on black wire

Reading is 4.95v on green wire

 

[ashleyroachclip]

That reading is for the signal wire , try the signal return wire .

 

[Tbrake1978]

That reading is for the signal wire , try the signal return wire .

I have just about tried everything. I am now wondering if I actually have a bad TPS

 

[MG0h3]

That’s possible.

Does anything happen when you play with the throttle or adj the TPS?

Make sure you don’t have a short to the 5V ref


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[Tbrake1978]

That’s possible.

Does anything happen when you play with the throttle or adj the TPS?

Make sure you don’t have a short to the 5V ref


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Nothing happens. I am into the wires for sure on the green wire and the black wire. I am getting 4.92V. There was 1 time I was able to get it to read .80 and it fluctuated to 1.11 but it was a brief moment and cant get it to read that again. If I am on the bare wires, I should get the .60-.98 reading correct? If I am constantly getting 4.92V does that mean that the TPS is bad?

Is there a way to test the sensor itself unplugged?

 

[ashleyroachclip]

All of the sensors use a 5.0 volt referance, .
Check you iac , look for 5.0 volt referance.
In theory you should have 5 volts from there to the tps on the reference wire .

I personally use the battery for my ground, when checking these .
I am suspecting there is nothing wrong with the tips.

 

[Tbrake1978]

All of the sensors use a 5.0 volt referance, .
Check you iac , look for 5.0 volt referance.
In theory you should have 5 volts from there to the tps on the reference wire .

I personally use the battery for my ground, when checking these .
I am suspecting there is nothing wrong with the tips.

I do get 5v on the orange wire and the green wire but everyone on the thread is saying the green wire is supposed to be less than 1V. I cannot get that reading. I just ordered a new TPS. To make sure I have a good connection, should I go ahead and bare the wires to get an accurate reading?

If it isnt the TPS, then what else could it be?

 

[Tbrake1978]

The main reason I was checking the TPS volt range is because the car will idle just fine and then all of the sudden it will just start surging bad to where it will sometimes die and other times it will go back to normal and idle correctly again. I have a tune scheduled for Thursday and am wondering if they will be able to figure out if and where there is a problem whether it be a vacuum leak or/and a sensor?

 

[MG0h3]

So your TPS is a potentiometer; the voltage signal changes based on throttle blade position. Max voltage is telling the ecm that you are WOT.

I’m curious if the voltage changes if you move the throttle blade or adjust the sensor.

I would remove it and make sure it is physically intact.

It’s also possible you have a short.

You should be able to do an ohms test with no power to the sensor.


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[Tbrake1978]

So your TPS is a potentiometer; the voltage signal changes based on throttle blade position. Max voltage is telling the ecm that you are WOT.

I’m curious if the voltage changes if you move the throttle blade or adjust the sensor.

I would remove it and make sure it is physically intact.

It’s also possible you have a short.

You should be able to do an ohms test with no power to the sensor.


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yep.I tried moving the throttle and no fluctuation on sensor voltage.

 

[MG0h3]

Ok so I’d take it off and make sure the tab isn’t busted.

Google an ohms test for it.

Also, try unplugging it and seeing if you still have 5v at the green wire on the car side


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