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Ultimate Throttle Position Sensor (TPS) Thread

291K views 188 replies 61 participants last post by  miesk5  
#1 · (Edited by Moderator)
PROBLEM: A number of months ago I discovered that my 86 Ford Full-size would hesitate/buck after about 10-15 minutes when the engine was at operating temperature. It would idle smooth and run fine until it hit 2000-2500 rpms...cruising speed.

So after reading many threads, I decided that the truck needed a tune-up. So I replaced cap and rotor with MSD, plugs, plug wires (Ford 9 mm) and even decided to go with a higher performing coil (Accel Supercoil). I also did the Seafoam thing (see my write up). It ran smoother but I would still get the hesitation/bucking.

BACK TO THE DRAWING BOARD: Started reading more threads on TPS, IAC and MAP. Decided to clean the IAC...someone on here had a great write up...search if your are interested. No change..smoother idle though!

Prior to removing the TPS, remove the negative battery cable. Some truck years will require that you scribe a mark across the sensor and the TB to ensure that the new sensor is installed in the same exact location. I was not sure about my truck so I did it anyway.
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DIAGNOSIS: Decided it must be TPS...yeah I know...look for codes. This time I did not have too! See below if you even suspect you have a TPS issue. There is a voltage test you can perform to determine if the TPS is within normal oerating ranges.

First you will need to locate the TPS and plug.

Plug

The TPS is located on the end of the throttle shaft on the throttle body (TB). By monitoring the output voltge from the TPS, the PCM can determine fuel delivery based on the throttle valve angle. A broken or loose TPS can casue intermittent bursts of fuel from the injector and/or an unstable idle. Any problems with the TPS will throw codes 23, 53 or 63 for the two digit system or 122 through 125 for the three digit code system.

TO CHECK THE TPS: Turn the ignition to ON (engine not running) and install the probes of the volt-meter into the ground wire (black) and the signal wire (green) on the backside of the electrical connector. This process is called BACKPROBING. Turn your key to the on position (the engine need not be running to perform this test). Your meter should read 0.50-1.0 volts at idle. FYI...because the black probe kept on sliping out of the back of the plug I grounded it to the battery, which works just fine aso.
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Rotate the throttle to the full-open position and the sensor should increase voltage to 4.0-5.0 volts. The maximum voltage I got was 1.85 volts. So I was for sure this must be the problem. Many have said that if you do not get a steady increase in voltage, this also is a sign of a bad TPS.

THROTTLE BODY REMOVAL: In most case you will need to remove the TB to get to the TPS. First remove intake hoses and the throttle cable assembly.
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The bolts that hold the throttle assembly (located on top of the intake) are 1/2"

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Next disconnect IAC plug, coolant hoses and vacuum lines. Remove the four bolts holding the TB to the intake. These bolts are 3/8".
This is the bottom of the TB where the TPS is located

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While you have this apart...check the intake and TB for crud build-up

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Mine was looking pretty nasty. Get some of this, a toothbrush and a rag and start cleaning it out:
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CLEAN TB AND INTAKE:
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Here is the new sensor to be installed...normal pracie was $54.99 my cost was $34.50, comes with a life-time warranty. While I was at it I decided to pick up a NEW Haynes manual. By the time it was all said and done I got the sensor and manual for original price of the sensor...christmas has come early!

INSTALL:
New sensor should be positioned the same as the old...wiring harness pointed away from the IAC. Engage the tanges of the sensor with the throttle shaft blade, then rotate it clockwise to align the reference marks before installing the screws.
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Reinstall the TB in reverse order. Make sure you hook vac lines, coolant lines and sensor wires up.

See Throttle Position Sensor (TPS) Overview, Test & Adjustment by Seattle FSB @
 
#3 · (Edited by Moderator)
Wow what a great thread! I have an 86 and I just figured out where the TPS is. I want to replace mine because I don't know how old it is but it sounds like you need to align the TB and TPS to function correctly not just replace the TPS, is that about it? I don't see a gasket on your TB is there supposed to be one?

Also, what type of metal is the TB made of, my cooling tubes are rusted. I want to know if these tubes are pressed in and can they be replaced or can I drill/tap in some threads and make them removable? Thanks!
 
#4 · (Edited by Moderator)
JKossarides said:
Wow what a great thread! I have an 86 and I just figured out where the TPS is. I want to replace mine because I don't know how old it is but it sounds like you need to align the TB and TPS to function correctly not just replace the TPS, is that about it? I don't see a gasket on your TB is there supposed to be one?
Also, what type of metal is the TB made of, my cooling tubes are rusted. I want to know if these tubes are pressed in and can they be replaced or can I drill/tape in some threads and make them removable? Thanks!
  1. 10th picture (after the spray cleaner) showsd the TB gasket. take it off before you clean the TB.
  2. I beleive some models you have to align correctly...nt sure if the 86 is for sure but I followed the directions just in case (marking the position)
  3. I think the TB is made of cast aluminum
  4. The cooling tubes are not aluminum...from the looks of my pics maybe they will screw out or gently pull out??? Maybe someone else has an answer to that. Are the tubes rusted on the outside? Holes in them? You could sand, prime, paint and if you wanted use a little POR15...but that is extreme and assuming that they are not rusted through. Good luck
 
#5 ·
Hey Xris 86 buddy thanks for the info, the bottom tube is working but it's condition is marginal and we all know that it's only a matter of time before something goes. I like to do preventative maintenance so the system is happier. I did a drill & tap with my cooling temp sensor so life is much easier if I have to repair being it is a bitch next the distributor so I don't have that problem any more. TB is aluminium OK, I don't want to spend $2-300 for a new TB so I'll look thru other threads to see if there are other tube solutions. Do you think they are Ford products? I'll check and if I found a company that makes them I'll post it. For the TPS replacement, I guess it wouldn't hurt to read the Haynes book right? THANKS BRO!
 
#6 ·
Excellent write up (and pics) Xris

I'm sure a lot of us 86ers are facing similar troubles.

Question for you; When you say

" Rotate the throttle to the full-open position and the sensor should increase voltage to 4.0-5.0 volts. The maximum voltage I got was 1.85 volts. So I was for sure this must be the problem"

Surely you don't mean with the engine on ?

Thanks again

Sixlitre

I'm having a starting and running issue lately. It's kinda crept up on me because I'm driving the old gal so little.

I have to use quick start to get her going. She just rolls over like she's getting no gas, until I shoot a little alcohol down her throats.

After she's warmed up she's sluggish at all stages of part throttle, like there's not enough gas getting to it, but goes gangbusters at wide open throttle.

To complicate things I busted that rod on top of the throttle body while fiddling around under that stupid plastic cover hat. Wouldn't you know it, the Ford replacement is plastic !!!!!!!!!

I'll be looking to score a real metal/plastic one, like in your pics asap at a junkyard.
 
#7 · (Edited by Moderator)
I hate when stuff like that happens when you're trying to be careful so as not to spend extra money when fixing a problem. Today I sprayed STP TB cleaner while she was running just to make sure it's a little cleaner and it seems to run a bit better. I think the cooling tubes on the TB may screw out, but I'm researching to make sure. I think I understand the TPS better, the throttle plates need to be closed before you install a new TPS so it will open to the right angle.

I have learned so much about my Bronco thru this site and I found it by accident. A plethera of information and all the money you can save by doing most of it yourself. I'm still laboring with my 02 sensor, what a bitch to get out. My buddy recommended Aero Croil deep penetrating to soak into the threads, who knows how long this one has been in there.

What about Sea Foam deep penetrtating? I figure anything to make it run better, gas prices are coming down, only $2.33 per gal today OUCH.
 
#8 ·
Sixlitre said:
Excellent write up (and pics) Xris

I'm sure a lot of us 86ers are facing similar troubles.

Question for you; When you say

" Rotate the throttle to the full-open position and the sensor should increase voltage to 4.0-5.0 volts. The maximum voltage I got was 1.85 volts. So I was for sure this must be the problem"

Surely you don't mean with the engine on ?

Thanks again

Sixlitre
Correct...In thought I had mentioned that but I'll have to look over the thread and do a possible edit.

Sluggish at mid-throttle...do you ever get bucking/hesitation at crusing speeds? Could be the TPS. I would do the electrical test or run the codes to find out. Six...its nice to see your still around!
 
#10 ·
Great close ups Pepe! Question though...how do you get a proper voltage check if the TPS is not connected to an electrical source? The plug is unplugged from the rest of the path...haynes suggests backprobing so there is that electronic stimulus. Let me know...Thanks Pepe!
 
#11 ·
OK I called Power Ford and they told me the cooling tubes in the TB are pressed in. So if anyone has actual experience in changing this tubes out please post. The only solution I can think of is to tap, thread and add new plumbing which would maker future repairs a snap as you wouldn't have to take off the TB the next time around and it's a whole lot cheaper then dropping $3-400 bucks for a new TB vs $1.00 for plumbing parts and engineering.

I keep forgetting to ask this question, what mm size is the stock TB for the 1986?
 
#13 ·
JKossarides said:
OK I called Power Ford and they told me the cooling tubes in the TB are pressed in. So if anyone has actual experience in changing this tubes out please post. The only solution I can think of is to tap, thread and add new plumbing which would maker future repairs a snap as you wouldn't have to take off the TB the next time around and it's a whole lot cheaper then dropping $3-400 bucks for a new TB vs $1.00 for plumbing parts and engineering.

I keep forgetting to ask this question, what mm size is the stock TB for the 1986?
Get to a junkyard

find a seized throttle body(they all seize when they sit) and offer the yard guy $25

Go home, clean and unseize it and away you go !

Sixlitre
 
#14 ·
Thanks Sixlitre, certainly that's an option I will consider but then the only problem is, can I find one where the cooling tubes are in better shape otherwise I'm right back where I started with the rust etc. I will check around the salvage yards out here and see what's available, this stuff doesn't last long out here, you know everything gets picked clean. Tapping threads in isn't the most difficult thing to do either so it's just a matter of time well spent for me. Thanks!
 
#15 ·
While we're talking about cleaning and testing TB's etc. I came across this product today at Kragen. Berryman-B12 Chemtool for gas, injection, carb, oil $4.29 a can. Has anyone heard of or used this stuff, kinda looks and sounds like Sea Foam, $5.99 a can? PLease post. Thanks!
 
#16 ·
JKossarides said:
While we're talking about cleaning and testing TB's etc. I came across this product today at Kragen. Berryman-B12 Chemtool for gas, injection, carb, oil $4.29 a can. Has anyone heard of or used this stuff, kinda looks and sounds like Sea Foam, $5.99 a can? PLease post. Thanks!
Blow the 4.29 and let us know what y'all thank

Sixlitre
 
#19 ·
Tank - Check out Fordfuelinjection.com for the appropriate readings. I think they are on there. If I remember correct it should be around .90-1.00. Check the site.

Did a little checking .50-1.0 volts. You may have to adjust your tps position slightly. Check your haynes.
 
#20 ·
I'm trying to dail everything in before Smogorama at the end of this week.
I have a spare TB on the bench with the TPS still on and I'm trying to learn how to probe for voltage on the blade angle.

I have a Craftsman digital multimeter #82082 but I'm not sure which setting to use to see .95v closed to 4.5-5.0v WOT.
So which setting do I use, V-DC, V-AC, A-DC or OHM? I'm thinking V-DC with the Haynes by my side ~

This is my least favorite part, it's all greek or I'm dyslexic ~ :banghead

Thanks ~ :thumbup
 
#21 ·
Set the DVOM to read VDC. Attach the leads to it properly (I'm not even going to explain this one). Ground the black lead to a very good, steady, SOLID connection; alligator clips would be excellent for this. Push a metal clothespin through the green lead (I think :scratchhe I should know this, I just did it! lol ), then measure the voltage off of that. The trick is to make sure that the pin is conductive and making excellent contact with both the conductor and the probe. You should be able to dial in your TPS voltage. I usually suggest folks to set it to ~0.94V with the key on and engine off. This is a safe distance from 1.0V, and will allow for meter error, connection imperfections, voltage fluctuations, etc.
 
#22 ·
sigEpBlue:
I've read this thread and studied this thing so many times I have the concept down but poking around wasn't producing anything.
On my DVOM, V-DC there are 5 settings from top to bottom they range from 1000, 200, 20, 2000m,200m and the instructions say start with the highest setting and work down until you get results. I have the plug in probes so I'll work on this today until I get it right. It's begining to make more sense but I've never liked the electrical diagnosis part, sorry for being retarded ~ lol lol

Thanks Brother ~ :thumbup
 
#23 ·
Hey Koss - I tried looking back to find out what setting I used...I think I have close to the same meter as you also! If my old man memory serves me correct it was the V-DC setting 20. Good luck brother!
 
#24 · (Edited by Moderator)
Practicing today on my benched TB with the multimeter, probing the TPS connector but still not getting any readings and I've switched to every setting in V-DC, DVOM is brand new. The TPS was on there when it came from "scrappy86" so no matter what it should show some kind of a reading good or bad, no?

I've cleaned the TB carefully and thoroughly using TB cleaner only and lubing springs and linkage so everything operates fine. I even managed to scribe it and get the TPS sensor screws loosened without moving it with a tiny bit of PB Buster and a large phillips.

Using the probes (red/black) either inside the connector or grounding the black one I'm not getting a reaction ~

What am I missing here?

Thanks ~ :thumbup
 
#25 ·
Practicing today on my benched TB with the multimeter, probing the TPS connector but still not getting any readings and I've switched to every setting in V-DC, DVOM is brand new. The TPS was on there when it came from "scrappy86" so no matter what it should show some kind of a reading good or bad, no?
I've cleaned the TB carefully and thoroughly using TB cleaner only and lubing springs and linkage so everything operates fine. I even managed to scribe it and get the TPS sensor screws loosened without moving it with a tiny bit of PB Buster and a large phillips.

Using the probes (red/black) either insdie the connector or grounding the black one I'm not getting a reaction ~

What am I missing here?

Thanks ~ :thumbup
Are you saying that this thing (TB) is not hooked up to any power source? No completed elctrical path from the perspective of the TB and electrical system? I think that maybe your problem. If this thing is just sitting on the bench...no input, then there would be no path to measure closed to WOT.

Somone please correct me if I'm wrong and Koss let me know if this is/or is not the case. You may want to test it on the TB that is in your truck.
 
#26 · (Edited by Moderator)
If I disconnect the TPS on the truck the sensor wouldn't have any power to it only the harness side would if the key was turned on. The multimeter is battery operated for power source if the probes are inserted into the connector, I understand you can test for continuity when everything is connected but the only way you can adjust the TPS for the voltage setting is to take it off the truck, losen the 2 screws and turn that little dial in the center of the sensor that's attached to the blade. If the TB is on the bench with the TPS sensor attached I still should be able to probe the TPS sensor connector with the multimeter to see where it's at, no?

Otherwise, once you take the TB off the truck how would you know how to adjust the angle of the blade for proper V. setting?


I also have a question about one of your threads in the very begining but I'll have to copy the dialog and post it next, sorry!

Thanks ~ :thumbup
 
#27 ·
Xris:

This dialog is in the begining between the 14 & 15th picture regarding the actual replacement with a new sensor, after scribing.

"Engage the tanges of the sensor with the throttle shaft blade, then rotate it clockwise to align the reference marks before installing the screws."

I don't quite understand this part completely ~


Thanks, sorry for being so dense on this ~ :thumbup
 
#28 ·
A quote from my Chilton's manual:

"The TP Sensor has two versions, an adjustable and a non-adjustable; the difference being elongated mounting holes that allow the rotory sensor to be turned slightly to adjust the output voltage. The rotary TP sensor with round mounting holes are not adjustable".


JKossarides, it goes on to say:

"On 5.0L and 5.8L engines, position the TP sensor so that the pigtail points toward the IAC valve".

"Slide the rotary tangs into position over the shaft blade, then rotate the TP sensor CLOCKWISE only to the installed position. Failure to follow this step may result in high idle speeds for 5.0L and 5.8L engines".

I hope this helps.
 
#29 ·
Yep! My haynes was not specific in regard to the variability in TPS. I found out by installing the new one and reading other posts that mine was not adjustable afterward. The instruciton given in my thread is for the adjustable TPS.

Thanks Seattle FSB for clarifying.