Can someone verify what their truck is set at on their F250? My brother owns an excursion and I set mine to the same voltage that his was running at a while back and though the truck runs fine the truck is beginning to stall randomly while coming to a stop. The truck fires up just fine and idles without a problem. It's just annoying as all get out.

I cleaned my IAC last time and it seemed to remedy the problem (non ford IAC made the problem worse). It's been maybe 6 months and it's doing the same thing again. I plan to buy a new FORD IAC tomorrow, but want to verify the TPS is set correctly.

 

There's nothing to "set" on a TPS.

If it's the right part, isn't defective, and is installed properly, then it's "set" correctly.

If you've been fiddling around with it, back-probing the output and trying to adjust it for a certain voltage, you've been wasting time since that doesn't do anything as the PCM recalculates the TPS threshold every time the engine is started.

 

Hmm, not accurate and not what I asked... Thanks for trying to provide helpful information.

However, your telling me if I was to loosen my tps and move it drastically one way or the other the car would idle just fine?

This is not the case as the TPS tells the pcm how much fuel the car needs based on how much throttle is being applied... If you think I am wrong, loosen your tps, start your truck and move your tps one way or the other and tell me your engine doesn't sound different.

TPS is a throttle position sensor... IE: You apply more throttle, more air comes into the intake thus the pcm tries to add fuel.

Just wanted to make it clear, the pcm may try and "correct", but it doesn't mean its ideal to just bolt on a tps and go.

Every car I have worked on has had a specific voltage recommended by the manufacturer. I don't have a manual in front of me, so I was seeking that information here.

 

Ah, but it is, whether you want to believe it or not. I know exactly what the TPS is, what it does, and how it does it. I'm telling you you're wasting your time dorking around with it except to perhaps verify it's within the proper range of .53 to 1.27 volts (straight out of the FACTORY documentation) at either KOEO or at hot idle.

I have the factory service manual right in front of me. It says to remove the old one and install the new one. That's all. There's no messing around with it in the manual.

Performing that procedure would be wrong because you're not supposed to be screwing with the sensor after the engine has already started (much less any other time). That only changes the input to the PCM AFTER the PCM had already set its baseline for subsequent calculations. Garbage in, garbage out.

Look, you can chase your tail all you want to. I'm just telling you that you're chasing your tail on this one.

 

I think the TPS is just a variable resistor attached to the throttle shaft.
The variable resistance provides a variable voltage.
The variable voltage the PCM reads gives the software an idea of what the throttle position is, but only a clue of what the airflow is.
Combined with readings from other sensors the software can calculate the optimum amount of fuel the engine needs.
At system power up a series of tests will check all the sensors and calibrate the system.
The voltage for the TPS will be regulated from the PCM as system voltage will vary depending on battery charge state.
The main difference between one TPS and another would be the mounting to a particular throttle body.
Each manufacturer will decide what voltage range they want to use for their software calculations and adjust the resistance range accordingly.
All of them are probably between .5v to 2v.
If the range of resistance for a 6.8L is .53 - 1.27v and the voltage never goes over 1v because of a bad TPS the calculations will be affected.
At startup the PCM only sees the minimum voltage and has no idea what maximum voltage the TPS will output.
Once a TPS is designed for a particular engine no adjustment is needed, just replace it with a new one.
I've installed 4 IAC valves, non-Ford, in various engines and all have worked fine.
Maybe with a new IAC the problem you are having became more pronounced.
When a vehicle is coming to a stop and the engine is decelerating the vacuum is high, maybe the problem is vacuum related.

 

TPS is actually a potentiometer not a resistor.

Isnt all this TPS adjustment action for the 80's and 90's?

Laslty i I haven't worked with a TPS since the 90's , but back then they did require testing and adjustment. i understand maybe the computer can adjust for closed throttle positioning but how can it know the full sweep if not for adjustment?

 

That is what I am wondering also. In old 5.0 mustangs the closer you got to 5 volts but not over was noticeably better for performance. Another check was to make sure you were WOT when the pedal was on the floor.

Analog voltmeter is the best way to check the sweep. It will show anomalies that a digital won't.

 

A potentiometer is a variable resistor.
The Throttle Position Sensor for a 6.8L Excursion is a Motorcraft DY967.
They are an R&R item.
Symptoms of a bad or failing Throttle Position Sensor include lacking power when accelerating, rough or slow idle, stalling, inability to shift up, and the service engine light coming on.

 

I am not as familiar with our V10 systems as the old 5.0.

Are you saying that loosening the screws and twisting the TPS one way or the other will have no effect? I am certain the TPS is not a net fit without some slop in the screw holes.

 

Twisting the TPS on loose screws probably would have some minimal effect.
I think it is intended to be removed and replaced with no adjustments.

 

I believe that is exactly what I said earlier.

 

You argumentative people have ruined the internet as a resource. Not one person considered answering the question. You just tried to prove your right. Oh, by the way. Your all wrong.