Tricks for setting TPS voltage?

87MustangGT said:

I used to be pretty good at (re)setting my TPS whenever necessary... Apparently letting the car sit for 5 years either made me very rusty, or there's actually something wrong with my TPS. Either way, I can't get my TPS to set right.

For about two weeks, I couldn't get it any higher than 0.08v. I tried for the first time in about 2 weeks, and I was able to get it up to .7-.9! But the sensor was tweaked so much that the holes on it weren't lined up with the holes on the TB. So I moved it back slowly, and now the most I can get (when the bolt holes line up) is 0.20v.

Any tips/tricks for setting this bad boy? The holes are already elongated, but I imagine I could drill them out a bit more.

TIA

Click to expand...

Most of us have to drill them some. You sure your throttle adjustment screw is not out of range. That will cause the throttle blade shaft to tunr and could be your issue.

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.

Wire colors & functions:
Orange/white = 5 volt VREF from the computer
Dark Green/lt green = TPS output to computer
Black/white = Signal ground from computer

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.

When you installed the sensor make sure you place it on the peg right and then tighten it down properly. Loosen the back screw a tiny bit so the sensor can pivot and loosen the front screw enough so you can move it just a little in very small increments. I wouldn’t try to adjust it using marks.

A.) Always adjust the TPS and Idle with the engine at operating temp. Dive it around for a bit if you can and get it nice and warm.

B.) When you probe the leads of the TPS, do not use an engine ground, put the ground probe into the lead of the TPS. You should be connecting both meter probes to the TPS and not one to the TPS and the other to ground.

C.) Always reset the computer whenever you adjust the TPS or clean/change any sensors. I just pull the battery lead for 10 minutes.

D.) The key is to check the TPS voltage whenever the idle screw is changed.

TPS testing:
Most of the time a failed TPS will set code 23 or 63, but not always. Use either an analog meter or a DVM with an analog bar graph and connect the leads as instructed above. Turn the ignition switch to the Run position, but do not start the engine. Note the voltage with the throttle closed. Slowly open the throttle and watch the voltage increase smoothly, slowly close the throttle and watch the voltage decrease smoothly. If the voltage jumps around and isn’t smooth, the TPS has some worn places in the resistor element. When the throttle is closed, make sure that the voltage is the same as what it was when you started. If it varies more than 10%, the TPS is suspect of being worn in the idle range of its travel.

TPS Troubleshooting:

The TPS sensor is a variable resistor like the volume control on most cheap radios. We have all heard them make scratchy noises as you turn them up or down. The carbon element can wear and cause a drop out spot in the output voltage. This confuses the computer because it expects to see a steady TPS voltage increase as the Throttle opens up.

Wire colors & functions:
Orange/white = 5 volt VREF from the computer
Dark Green/lt green = TPS output to computer
Black/white = Signal ground from computer

TPS troubleshooting steps:
1.) Use the Orange/white & Black white wires to verify the TPS has the correct 5 volts source from the computer.
Use the Dark Green/lt green & Black/white wires to set the TPS base voltage. 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.
2.) Use an analog voltmeter to check the voltage on the Dark Green/lt green & Black/white wires to make sure that it increases smoothly and doesn’t drop out or increase suddenly.

Some basic checks you can make to be sure that the sensor is getting power & ground:
Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter.
Check the resistance between the black/white wire on the MAP/BARO sensor and then the black/white wire on the EGR and the same wire on the TPS. It should be less than 1 ohm. Next check the resistance between the black/white wire and the negative battery cable. It should be less than 1.5 ohm.

The following power on check requires you to turn the ignition switch to the Run position.
Use a DVM to check for 5 volts on the orange/white wire. If it is missing, look for +5 volts at the orange/white wire on the TPS or EGR sensors. Use the black/white wire for the ground for the DVM.

I would just stick the TPS on top of the TB. Make sure the shaft is in a spot to turn the TPS. put your screws in and screw them on but dont tighten them yet.

Clock the tps to get your voltage, when you do, make sure you hold it tightly while you tighten the screws.

that way the screws are already in when you adjust it.

and recheck when the TPS is on completely

Time to replace it. Its has slowly been deteriorating, and slotting the holes was just bandaiding the issue.

then you got wiring issues if this also happened on a new TPS or you are doing something wrong

I had mine at .6x and I would let off the gas to coast then press the pedal and nothing would happen. Then all of a sudden it would kick in. It was a good sec pause. I elongated the holes to get to .9x and the car stopped doing it. Maybe it was something else but that was my experience with the TPS.

If this is a new TPS, then its time to check the reference voltage between the orange and black wires. That should show 5v. JR has pretty much outlined that. Also, since you are checking voltages using the black wire as ground, try using a body ground. If your voltage now shows a none failure code voltage, then the issue is within the ground circuit. That's assuming you have the 5v previously mentioned. If the 5v is absent, then its time to go over the 10 pin connectors as all the circuits for the TPS passes through them.