TPS voltage / Plenum & TB Install

Anyone know what the voltage should read at WOT? I've got the Accufab TB/Plenum on the way and I just read some plenum/tb install instructions in the latest 5.0 magazine and it mentions you need to set the tps voltage with a digital voltmeter. Any help on the procedure and voltage specs would be greatly appreciated!

downsouthman1 said:

Also, a digital voltmeter can't set any voltage, only measure it.

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Correct - that's what i meant - use the digital voltmeter to check the tps, not "set" it. Sorry for the mis-play of words. From my understanding, our stangs do not have adjustable (rotate-able) TPS's. However, if I have the TPS off, I figure it wouldn't hurt to check it's operation to make sure it's operating properly. So does anyone know the WOT voltage? I'm going to venture a guess that it's probably 1.0 volt. . . but I honestly don't know if it's similar for all cars.

GinoGT said:

Idle is like .96-.99 volts. WOT should be near 5 volts, but it mine only goes to like 4.6 or something like that.

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Thanks. I'll probably check the TPS both before I remove it from the stock TB and after just to make sure it's at least operating over the same voltage range as currently.

I would also think the TPS is part of the EEC, so if it wasn't working properly you'd think you would get an MIL.

OK, I'm getting confused again. Here's what I've got so far:

1.) You CAN actually adjust the TPS on a 99+ mustang, but the adjustment is minor.

2.) The digital voltmeter test should be performed when the tps is attached to the TB (makes sense.)

3.) The voltage at idle should be approximately 1; the voltage at WOT should be ???? This post has a range of 4.28 volts to "I have no idea" to 5 volts.

Does anyone know for certain what the WOT voltage should be on the TPS? Are any of these items I listed incorrect?

Sorry to keep bumping this post, but I really want to get to the bottom of this. When I first asked about setting the TPS / checking the TPS voltage a while back, most people said there was no adjustment available and you just slap the TPS on the TB. Now, I'm getting mixed opinoins. It funny how there must be 1000 threads on CAIs, but when you get down to something a little more technical, the audience becomes much smaller!

Thanks for the replies - please keep them coming so we can get to the bottom of this.

MT1083 said:

Can you call Accufab so you can get a correct answer?

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Good idea. . . first, here's what they have on their website:

"How tough is the Accufab throttle body to install? Not very. In most cases, all you will need to do is to remove the old (or stock) throttle body and replace it with the Accufab throttle body. Our throttle bodies are designed to bolt to the original manifolds, in the original location using the original bolts. No grinding, beating, filing, or other fabrication is required. Typically, throttle bodies have a throttle position sensor (TPS) bolted to them. Simply unbolt the sensor from the old throttle body and bolt it on to the new one. You will need to insure that the TPS is accurately adjusted to insure a good idle. This is easily done using a Voltage Meter. You are looking to set the TPS between .98 and 1.0 volts measured between the hot wire and the ground wire. Also, the throttle stop on the throttle body has been pre-set at Accufab and does not require any adjustment. It can’t get easier than this. Same with the throttle cable. The Accufab throttle body is designed to accept the same OEM cable mechanism in the same location."

This still wasn't entirely clear to me so I called Accufab and spoke to a nice and helpful guy named George. Here were my questions and his paraphrased responses:
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1.) Do you need to set the TPS on a mustang when swapping TBs?

Yes, but it isn't that technical. If you wanted to run through Ford's established procedures to set the TPS at idle, you'd use a voltmeter and set the TPS to where the voltage reading was between .98 to 1.0.

2.) How do you set the TPS to .98-1.0 at idle if the TPS is essentially non-adjustable?

There is some (albeit a minor amount) of play in the TPS when the TPS bolts are loosened a little. This minor amount of adjustment should allow you to properly set the TPS at idle. We actually don't even use a voltmeter when setting the tps - you can essentially go by the idle speed of the motor. If the idle is too high or low, rotate the TPS one way or the other until the car settles into a nice steady factory-spec idle (I think George said it was between 650-700 but I can't remember exactly what he said.)

3.) Do you need to set the TPS at WOT?

no, it is what it is. In most cases, you can just swap the TPS without even checking the voltage and it should be just fine / within spec.

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So, it looks like everyone is correct! Sounds like if you installed your new TB and your car has a good idle but you never set the TPS, it's likely that you didn't need to in the first place. I think this is probably why most people don't have problems with a TB swap even if they didn't set the TPS because chances are it's already close/at spec. However, if anyone's ever swapped their TB and is suddenly having minor idle problems, you might look to the TPS and check it with a voltmeter to ensure the idle setting is between .98-1.0 volts.

Cool . . . thanks for guiding me down this road. Incidentally, George said the TB/Plenum is the real deal and you will "feel" the power increase . . . not that he'd say otherwise, but I'm still excited to install my new Accufab Plenum/TB this weekend!