Throttle position sensor question [TPS] - TCCoA Forums
 
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post #1 of 7 (permalink) Old 08-14-2014, 12:54 PM Thread Starter
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Throttle position sensor question [TPS]

i believe this is my tps?


bad tps symptoms include hesitation during acceleration [what i have]

how to trouble shoot it...
http://easyautodiagnostics.com/ford/...nostic-tests-1

Last edited by blinky99; 08-14-2014 at 03:38 PM.
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post #2 of 7 (permalink) Old 08-14-2014, 01:43 PM
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Wrong.
What you have labeled as the MAF is your idle air control valve. The IACV lets in more air when the engine is cold and can cause rough idle or high idle issues depending on how its stuck. The MAF is actually the big metal can shaped item right after the airbox.

It's hard to tell but the TPS looks like it's labelled correctly (it sits on the side on the same plane that the throttle body butterfly -- and it shaft goes through).

If you unplug the TPS, the computer will still know how mcuh air is coming into it (from the MAF) but wont know WHICH fuel map to use (The one for WOT or the one for cruising). Hence, it drives roughly because it doesn't know what is actually happening to the car (is the car accelerating or just driving at steady state at a higher speed).

The proper way to see if the TPS works is to measure the voltage from it. Use a paperclip/pin to read the voltage on the right pin from behind. You'll have to figure out which pins to use (one is ground, on is input 5V, and the other is the output signal).

At closed, it should read 0.75V or thereabouts. At full open, it should be closer to 5tV. Your car doesn't need to be running but the electrical system shoudl be on for this testing.
-g

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post #3 of 7 (permalink) Old 08-14-2014, 02:25 PM
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The plug in the last pic is unused unless you have the dummy light module(aka VMM) in the lower DIN slot below the stereo. There should be another unused plug in the same area for the V8 coolant reservior

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post #4 of 7 (permalink) Old 08-14-2014, 02:34 PM Thread Starter
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ty-

Quote:
Originally Posted by S4gunn View Post
It's hard to tell but the TPS looks like it's labelled correctly (it sits on the side on the same plane that the throttle body butterfly -- and it shaft goes through).

If you unplug the TPS, the computer will still know how mcuh air is coming into it (from the MAF) but wont know WHICH fuel map to use (The one for WOT or the one for cruising). Hence, it drives roughly because it doesn't know what is actually happening to the car (is the car accelerating or just driving at steady state at a higher speed).

The proper way to see if the TPS works is to measure the voltage from it. Use a paperclip/pin to read the voltage on the right pin from behind. You'll have to figure out which pins to use (one is ground, on is input 5V, and the other is the output signal).

At closed, it should read 0.75V or thereabouts. At full open, it should be closer to 5tV. Your car doesn't need to be running but the electrical system shoudl be on for this testing.
-g
Right i found the diagnostic procedure here for TPS
http://easyautodiagnostics.com/ford/...nostic-tests-1

update:
-ok test 1, part 1 reads .88 DC volts, which is within range according to testing procedure i linked.

- test 2 , reads 5.14 dc volts, above range given in testing procedure

-ok interesting TEST 3: Ground Circuit Test fails
it read 12 volts
test i did >http://easyautodiagnostics.com/ford/...nostic-tests-2

"CASE 1: If the multimeter showed 11 to 12 Volts, then the PCM and the wire/circuit (that supply this ground) are OK.

This multimeter test result also confirms that the TPS sensor is BAD and needs to be replaced, since you have verified that the TPS is not producing a signal and does have power and ground."


but step 2 of part 1 i dont understand...
"slowly rotate the throttle manually while you observe your multimeter.
For this test result to be accurate, you need to rotate the throttle by hand and not from inside the car or mini-van.
"
- i dont see how to rotate it..?

also form part 2 step 1 "As the throttle opens, the voltage reading should increase smoothly and without any gaps or skips. Once the throttle is wide open, your multimeter should read about 4.5 to 4.9 Volts DC"


would this part fit my symptoms?

from dead stop to quick acceleration- car hesitates
from dead stop BUT slow accel -no problems
but at cruising speed 25 mph or so to acceleration [i.e mash the gas pedal] -no problems
also if i slow to a near stop 5-10 mph then accelerate to 30mph or so - no problems

Last edited by blinky99; 08-14-2014 at 05:20 PM.
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post #5 of 7 (permalink) Old 08-14-2014, 03:11 PM
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Quote:
Originally Posted by blinky99 View Post
but step 2 of part 1 i dont understand...
"slowly rotate the throttle manually while you observe your multimeter.
For this test result to be accurate, you need to rotate the throttle by hand and not from inside the car or mini-van.
"
- i dont see how to rotate it..?

also form part 2 step 1 "As the throttle opens, the voltage reading should increase smoothly and without any gaps or skips. Once the throttle is wide open, your multimeter should read about 4.5 to 4.9 Volts DC"

[/b]


Let's start with what a throttle position sensor does. It tells the computer how far open the throttle is.

Your accelerator pedal is connected to a cable.
The cable connects to the throttle body.
As you put your foot down, the throttle cable tugs on a lever which makes the butterfly inside rotate.
The TPS is connected to that same shaft.
When the instructions say for you to manually rotate the throttle, it means to manually pull that lever. THis is also the left you push on when you want to rev your engine from underneath the hood.

Go look at your car with the plastic intake tube temporarily removed. You will see how it works.

If the voltages are slightly off, you can adjust things slightly by loosening the mount bolts for the TPS sensor and rotating it slightly before tightening it down. This will raise/lower the base reported voltage (for when the TB is closed).

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post #6 of 7 (permalink) Old 08-14-2014, 03:19 PM Thread Starter
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ty again

Quote:
Originally Posted by S4gunn View Post
When the instructions say for you to manually rotate the throttle, it means to manually pull that lever. THis is also the left you push on when you want to rev your engine from underneath the hood.

Go look at your car with the plastic intake tube temporarily removed. You will see how it works.

If the voltages are slightly off, you can adjust things slightly by loosening the mount bolts for the TPS sensor and rotating it slightly before tightening it down. This will raise/lower the base reported voltage (for when the TB is closed).

i understand the lever you are speaking of...

-tested this it goes from .88 to 4.6 wide open when i slowly push the lever with engine off key on position. it' seems pretty smooth,
-i also did test 1 part 3 where you tap on the TPS it and watch the volts rise/fall still smooth.

i updated my post above with the latest test [ which is test 3], which is leading me to believe that the TPS is bad.

-ok interesting TEST 3: Ground Circuit Test fails
it read 12 volts
test i did >http://easyautodiagnostics.com/ford/...nostic-tests-2

"CASE 1: If the multimeter showed 11 to 12 Volts, then the PCM and the wire/circuit (that supply this ground) are OK.

This multimeter test result also confirms that the TPS sensor is BAD and needs to be replaced, since you have verified that the TPS is not producing a signal and does have power and ground."

Last edited by blinky99; 08-14-2014 at 07:01 PM.
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post #7 of 7 (permalink) Old 08-19-2014, 11:08 PM
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Quote:
CASE 1: If the multimeter showed 11 to 12 Volts, then the PCM and the wire/circuit (that supply this ground) are OK.

This multimeter test result also confirms that the TPS sensor is BAD and needs to be replaced, since you have verified that the TPS is not producing a signal and does have power and ground.
Quote:
-ok interesting TEST 3: Ground Circuit Test fails
it read 12 volts
You got 12 Volts - so the PCM ground curcuit is GOOD.

The test result says "the TPS sensor is BAD since have verified that the TPS is (1) not producing a signal and (2) does have power and (3) [does not have] ground" - this conclusion that the TPS sensor is bad - does not apply - because your testing passed all three tests. Right?
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