TPS Issues

[Powerpat]

I have replaced the TPS sensor and still get the same error at approximately 2.0v. The meter read OL at 2.0v only otherwise the readings are good from 1v to 4.8v. I also replaced the entire throttle body and had the same error. Any thoughts? Could it be something in the ECU?

 

[fastpakr]

Can you start back at the beginning? Out of context I'm not quite sure what's going on here.

What is the error?
What problem are you trying to solve?

 

[RonD]

Test with OHM meter as well, ohms get lower as throttle opens

When throttle is closed you should read .69-.99volts, just under 1 volt
Wide open above 4.5volts

No sure what "OL" means on your meter, is it set for 20vDC, so OL means over limit, i.e. higher than 20vDC???, which is not possible in a vehicle with 12volt battery and under 15v running voltage

Computer has a 5volt power supply, it is used for several sensors, MAF and TPS both share that 5volt wire from computer
That is called a Reference voltage so doesn't have to be exactly 5volts, 4.8 to 5.2 is fine

Then computer has separate Return voltage wires from TPS and MAF, in this example.
As you open throttle, TPS variable resistor gets less and less resistance(lower OHMS) so voltage on Return wire goes up, this is same as light dimmer or volume control work.
Computer then compares the difference between Reference Voltage and Return voltage to get throttle position.

I can't see the computer being the problem because it would be a constant problem, it shouldn't occur at a specific throttle position, electrically the only change is the OHMs at TPS, should be any change in the computer end by moving TPS

The two center wire on MAF use the 5volts, see which one is 5volts, key on, and which is the Return wire, the one that not 5volts
Test the Return wire as you open TPS see if it is effected, its a separate circuit but just looking for possible computer issue.

1993 means computer is 25 years old, and these computer do have 3 blue capacitors that can leak, which can cause very odd issues, which your is

You can see them in this picture: http://www.auto-diagnostics.info/ford_eec_iv

They are cheap and not too hard to change, under $5, if you can desolder and resolder in new ones.
So after exhausting other options pull out computer and open the top to see if Capacitors are the problem, you will see black residue under a leak capacitor

 

[Powerpat]

I have a misfire while driving the truck. So I decided to check the TPS sensor to see if it was bad. The original TPS would overload according to the volt meter at 2 volts. So i replaced the TPS with a new one. Tested it and found it was still having the same problem. Then i replaced the entire throttle body with another unit to see if this would correct the problem but it still overloaded at 2 volts.

The only hiccup is at 2 volts. It reads 1 volt in the closed position and 4.8 volts wide open throttle.

I have posted a video on you tube of the meter readings: https://youtu.be/jdT0JOZz7SQ

 

[fastpakr]

I have a misfire while driving the truck. So I decided to check the TPS sensor to see if it was bad. The original TPS would overload according to the volt meter at 2 volts. So i replaced the TPS with a new one. Tested it and found it was still having the same problem. Then i replaced the entire throttle body with another unit to see if this would correct the problem but it still overloaded at 2 volts.

The only hiccup is at 2 volts. It reads 1 volt in the closed position and 4.8 volts wide open throttle.

I have posted a video on you tube of the meter readings: https://youtu.be/jdT0JOZz7SQ

Interesting. And OL definitely means overload on that meter? I'm curious if it's more of a loss of signal at that point, that somehow the resistance goes infinite for a brief point in the sweep of the TPS unit. That wouldn't explain two TPS units giving the same results. Would be interesting to see what an analog meter shows at the same point.

 

[Powerpat]

One other important part I forgot to mention is that this is a turbo motor swap from a 1988 thunderbird. So there is no MAF. I would have to check it at the Barometric Pressure Sensor for another reference.

 

[kimcrwbr1]

Are you getting multiple fault codes? Always address the lowest number first. If it is missing a input for the ecm you may need to get the correct computer for that system. It may require the proper harness as well.

 

[RonD]

Wiring diagram here: http://therangerstation.com/tech_library/pdf_documents/88Thunderbird-turbowiring.pdf

select DC Volts touch probes together what does it show in display?

Can't understand OL designation, can you look up Meter's manual on-line and see what it means

Can't be high voltage since it doesn't exist in a Ranger, or most vehicles

 

[tomw]

On all the DVOMs I have seen, OL is a 'resistance' reading, not a voltage reading output.

From what I understand it means 'open link'. FWIW.

With an analog VOM, you should see a relatively smooth change in resistance as the TPS is moved through its sweep.

They can develop 'dropouts', even with low mileage. If you had an automatic with a lock-up torque converter, a faulty TPS can cause the transmission to un-lock the converter, and then re-lock without change in accelerator pedal position. Hidden feature.
tom