Ultimate Throttle Position Sensor (TPS) Thread - Page 5 - Ford Bronco Forum
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post #81 of 185 (permalink) Old 02-22-2009, 07:02 AM
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Something I will add that may help some. If for some reason your TPS is indeed returning ~5Vdc with the throttle closed, then the truck will either be incredibly hard to start, or impossible to start. This is because the ECM has a "flood clear" program that is run if it reads WOT during cranking. It works the same way that it did when cleared a flooded carbed motor. The ECM reduces the injector pulse width to near 0% duty cycle until the operator gets off the throttle, or the ECM detects a steady PIP indicating that the engine started. You will normally be able to start it on secondary fuel (propane, starting fluid, gas in the intake, ect...) and get it to idle but it will be a rough idle and rich as hell and typically not drivable.

Point is, if you get a ~5Vdc reading, and yet you can still get the engine to start normally and run, then Sig is correct, you measured wrong. The only reason I bring this up, is it happened to me on my fuelie 460, the TPS got stuck at WOT and nearly stranded me getting ready to load the SOB on the trailer for a wheeling trip. This may not apply 5.0 and 5.8 TPS but appears to be nearly identical to 460 TPS. On the 460, the TPS is opened by the tang on the TB, but relies solely on it's spring to return to idle position-- meaning there is only POSITIVE engagement with the TPS in the opening direction, if it sticks, it is free to stay stuck open.

The OP did a good job of explaining the testing procedure. The Haynes details it very well also. Some of the stuff coming later in the thread is not going to do a damned thing for you. One guy showed the harness unplugged and checking two of the wires with a meter in diode check mode??? WTF, that is not going to do anything for you at all. Checking the TPS on the bench? Not going to work, it requires a regulated 5Vdc reference voltage, the multimeter's batteries aren't going to do it, nor is it meant to be a power source. You can check the resistance of the TPS on the bench with a multimeter, but none of the common test procedures list the resistance range of the sensor, so it won't give you any really usable data. Learn how to use your test equipment, there is a wealth of knowledge on how to properly use a multimeter on line. If you saw the need to buy it, then do yourself a service and learn how to use it.

Later,
Jason

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post #82 of 185 (permalink) Old 02-22-2009, 08:33 PM
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Quote:
Originally Posted by SigEpBlue View Post
You're measuring it wrong. One line is VREF (Brown/White), another is SIG RTN (Gray/Red). Don't pay any attention to the colors on the TPS, but instead look at the actual engine wiring harness. Between those two there should be +5.00V, or within +/-0.05V of that. None of these measurements should be made relative to chassis ground; the sensors are on their own little circuit, as the PCM only looks at the voltages coming back to it relative to those two levels only (not chassis ground, battery positive, etc.).

You should be putting your DVOM's negative lead to the SIG RTN line, and the positive lead to the TP line (Gray/White).
I don't have wires going to the TPS module that match the colors you describe. The wires going to the TPS plug on the factory harness side are orange/white, black/white, and green/white. This matches the 1987 chassis electrical diagram in my Chilton's manual. If I reference the 1994-1995 diagram I find that the wires correspond as follows:
Gray/white = green/white going to ECM pin 47
brown/white = orange/white shared with MAP sensor, EVP sensor, going to pin 28
Gray/red = black/white

So, I should be measuring voltage with my green/white wire as the (+) and my black/white as negative.

Here's the voltages I'm seeing:

Measuring the voltages (throttle closed then throttle WOT)
20 v scale (shows 12.00 with battery voltage)
Green/white (+) black/white (-) .00 closed .04 WOT

2 v scale (shows 1. with battery voltage)
Green/white (+) black/white (-) .000 closed .037 WOT

I'm not seeing anything close to the 5V everyone is citing. If I use a chassis ground for the meter (-) I get 5.02 volts at idle position, and 5.09 volts at full throttle position on the TP wire. The orange wire consistantly reads 5.10 volts regardless of throttle position.

Keep in mind that my truck does start and drive, there isn't a no start or hard start issue. Any idea what I am doing wrong? The OP said the chassis ground was ok to use.
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post #83 of 185 (permalink) Old 02-22-2009, 09:31 PM
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Well, barring a wiring harness fault, it's starting to sound like a problem in the PCM. I would look very hard for a wiring fault, though. I don't care what anyone says, chassis ground is not SIG RTN. Chassis ground is NOT what the PCM is looking at when it's converting analog voltages to digital values.

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post #84 of 185 (permalink) Old 06-08-2009, 08:57 PM
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I finally got around to getting the TB off. I have it cleaned and the IAC wiped down. I got the old TPS off but the screws had no heads on them. There are two studs threaded into the TB for the sensor to fit over. The old sensor was most definetly stock cause it had a good amount of the epoxy(not extremely hard though) covering the back...including filling the screw holes. I am going to attempt to get the studs out tonight and get the appropriate screws(with heads and washers) to reinstall everything.

I am wondering if anyone knows what the thread count is on these screws that holds the TPS to the TB? I am going to guess they are in either 8/32 or 10/32 ,but not sure. I will take them to the hardware store and check the threads if there are any left after removal.

Thanks for any help,
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post #85 of 185 (permalink) Old 06-08-2009, 11:51 PM
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Quote:
Originally Posted by gunterelectric226 View Post
I finally got around to getting the TB off. I have it cleaned and the IAC wiped down. I got the old TPS off but the screws had no heads on them. There are two studs threaded into the TB for the sensor to fit over. The old sensor was most definetly stock cause it had a good amount of the epoxy(not extremely hard though) covering the back...including filling the screw holes. I am going to attempt to get the studs out tonight and get the appropriate screws(with heads and washers) to reinstall everything.

I am wondering if anyone knows what the thread count is on these screws that holds the TPS to the TB? I am going to guess they are in either 8/32 or 10/32 ,but not sure. I will take them to the hardware store and check the threads if there are any left after removal.

Thanks for any help,
Jeff
Jeff

The ex-act same thang happened to me. They were philips (star/cross) head screws.

I got them out, but like you, baffed the screw heads. The fastening store had what I wanted. Wish I could remember the screw size for you. Wonder if it's further back in this thread ?

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post #86 of 185 (permalink) Old 06-09-2009, 01:29 AM
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Six--- I got one out. The other broke off flush when I tried turning out with a pair of vise-grips.

I can tell you that it has got to be a metric thread cause it is a hair smaller than 8/32 but no where near 6/32. Definetly fine thread. I got the tap out and tapped the hole of the screw that came out(with out drilling). I had to drill the other out and tapped it to 8/32. I used a center punch to start the drill bit(got as close to center as possible) and drilled it for an 8/32 tap. I got through clean and very close to completely center of the old screw. tapped it to 8/32 and got two off the work truck. I have the new TPS is mounted ,the clean IAC is mounted(temporarily till I get a new gasket tomorrow).

I didn't spray either the TB or IAC with the throttle body cleaner. I sprayed an old rag and wiped everything by hand. I used sprayed q-tips to get the smaller areas. I am very happy with how clean I got it.

Bringing me to another question.....why the black and yellow sticker saying not to clean the inside of the TB??? I obviously didn't mind the sticker as I followed the many suggestions of fellow FSBers and very carefully cleaned everything.

I am going to try and replace the vac line that runs from the TB to the charcoal box(correct name?). The line seems to be ok but the rubber "boot" that fits onto the throttle body is a little dry rotted and don't see it being to bad to just replace. I had considered just cutting a 1/2" off the rubber boot end and letting it go.


Once again a very thorough write up that has helped me. My thanks for the guidance.


Jeff
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post #87 of 185 (permalink) Old 06-09-2009, 12:28 PM
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Quote:
Originally Posted by gunterelectric226 View Post

Bringing me to another question.....why the black and yellow sticker saying not to clean the inside of the TB??? I obviously didn't mind the sticker as I followed the many suggestions of fellow FSBers and very carefully cleaned everything.

Jeff
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Good on ya' getting them out and repaired. I don't remember nuthin' bout' them being French (metric) IIRC.

Dunno about the underside, but Ford would have you believe that their special no stick coating, on the inside, is still there after 24 years (in my 86's case) and we're not to use harsh cleaners on it.

Unless I'ze cautioned otherwise, by guys here, I'm planning on introducing all kinds of harsh chemicals to mine when I pull the heads off shortly(blown head gasket)

I want them lower and upper intakes gleaming inside before I pull em' back on. Might even re-locate the PCV nipple to the middle runner, as recommended.

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post #88 of 185 (permalink) Old 06-18-2009, 09:46 AM
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TPS question:

I'm retro-ing a 94 F150 with and E4OD: going back to a Holley carb and dumping the fuel injection. (serviceablity in the field) I'm gonna need to run a TPS connected up to the Holley. Whose been here before? Any suggestions on a workablde TPS for this setup? What about the TPS that came off this motor fuelie? I'm gonna try to make this work without running a Baumann Controls, but I have a feeling that is what's gonna have to happen. Appreciate some advice on this.

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post #89 of 185 (permalink) Old 06-22-2009, 12:35 PM
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My check engine light has been on since I bought the Bronc and I pulled the codes and got a 63,
which says is the tps. I looked at the tps and found this


The middle wire looks to be barely hanging in and the cover is pulled way back.
Will be hitting the parts place tomorrow.

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post #90 of 185 (permalink) Old 06-24-2009, 11:48 AM
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Changed my TPS yesterday and instant improvement in acceleration and smooth ride. But last night, the truck shuddered and the check engine light came on. Drove it a little while ago and it did fine for about 10 minutes but then, BOOM, same thing. Pulled the code and got a 63 which is what I got the other day before I changed the TPS. What could be the problem?

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post #91 of 185 (permalink) Old 06-24-2009, 11:56 AM Thread Starter
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Quote:
Originally Posted by Bronco325 View Post
Changed my TPS yesterday and instant improvement in acceleration and smooth ride. But last night, the truck shuddered and the check engine light came on. Drove it a little while ago and it did fine for about 10 minutes but then, BOOM, same thing. Pulled the code and got a 63 which is what I got the other day before I changed the TPS. What could be the problem?
Code 63 shows the following:

TPS low - Bad or misadjusted TPS, TB base idle mis-set, binding throttle cable

Not sure if the TPS is adjustable on the 90 bronco's..I would start there...if I recall correctly, the 86 was not adjustable. It was direct bolt in with no adjustment, although the haynes had procedures in regard to marking and aligning correctly.

Oncew you installed the new TPS did you take measurements again? Some have stated that even he new TPSs were bad.

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post #92 of 185 (permalink) Old 06-24-2009, 12:20 PM
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I don't have a volt meter to check the readings. The TPS I installed did not appear to be adjustable, meaning the holes were not ovaled. I've searched on the subject of throttle stop screw but could not find the method for checking to see if it is set corrrectly. Should've said it in previous post, but idle was around 1200 after installation of new TPS.

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post #93 of 185 (permalink) Old 06-27-2009, 04:43 PM
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To go along with this thread, frabicating a TPS back-probe adapter can make one's life much easier with reading the voltage.

cutting up a male and female parts and soldering the appropiate same colors back together




Using a voltmeter on the lowest setting and with alligators clips

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post #94 of 185 (permalink) Old 06-30-2009, 11:44 AM
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Took the truck to the shop and they hooked it up to a code reader. It showed 63, so the guy hooked up a volt meter to the TPS and got a 5.04 and there it stayed with the throttle open and closed. Does that mean he messed up? He said the TPS was bad.

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post #95 of 185 (permalink) Old 06-30-2009, 11:48 AM Thread Starter
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Quote:
Originally Posted by Bronco325 View Post
Took the truck to the shop and they hooked it up to a code reader. It showed 63, so the guy hooked up a volt meter to the TPS and got a 5.04 and there it stayed with the throttle open and closed. Does that mean he messed up? He said the TPS was bad.

Yep...check the beginning of this thread for the proper range. If the volt meter did not move through the range when opening the throttle then you have a bad TPS.

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post #96 of 185 (permalink) Old 06-30-2009, 12:51 PM
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When I took the old TPS off, the wires were facing away from the IAC so I installed the new one the same way. All the pics I've seen show the wires going toward the IAC. Which way is correct?

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post #97 of 185 (permalink) Old 07-03-2009, 08:24 PM
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O.K., went and got another TPS and put it on. Everything seems to be good so far. No check engine light, smooth idle around 850 to 900 RPM, and no more loping while driving. Keeping my fingers crossed.

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post #98 of 185 (permalink) Old 09-21-2009, 03:26 AM
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if i have time, i'm gonna check the voltage of the tps on my f150. it stalled 3 or 4 times on me sunday when i came to a stop and sat for a minute or more.

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post #99 of 185 (permalink) Old 09-22-2009, 01:33 AM
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ok guys i did something wrong. lol. I took my TB off and cleaned it. I replaced both the IAC and the TPS. I reassembled everything the way it was. Now everthing's back to normal as far as i can see but when i start the Bronco up (1991 EB 5.0) it immediately revs to 3k and won't go down. Any idea what i did wrong? I really appreciate the help!
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post #100 of 185 (permalink) Old 09-22-2009, 01:52 AM
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Check for vacuum leaks, and make sure the TP voltage is correct. It's easy to put the TP sensor in wrong by getting the tangs engaged improperly.

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