Throttle Position Sensor Screws and Adjustment

I am replacing my TPS with a re-manufactured unit.

Can anyone please tell me the proper driver bit for its mounting screws. Thank you.

The accelerator cable spool was standard Torx Security screws, but the TPS are weird. Original to the dealer replacement of the TB under warranty with sealing paint.

How does one clock the new TPS as it has some adjustment?

I will be using IDS to set the pedal once it is installed, however do I need to do another procedure before that such as battery disconnect?

Thanks.

 

5 point Torx.
I did with out IDS. If dies - rotate one way, if RPM too high - rotate the other way, keep doing until get to Goldilocks zone.

 

Thank you very much.

 

Update: A very XK8 knowledgeable friend has informed me that resetting the TPS sensor is properly a bench adjustment for the Throttle Body, and that anything performed on car is a compromise.

The consideration is then whether to leave the older unit in place and plan to send it somewhere for calibration.

Or, a question for the group:

Is there a particular function in IDS which can perform the "fine tuning", and does this negate or require some preliminary clocking of the sensor installation before doing so?

Some preliminary research has found that signal voltage is a factor in the sensor setting.

Thank you for all of your help.

 

The car's computer learns the new position - I can't see how doing it on the bench would work any better than pcolapacker's Goldilocks method. Depending on whether or not you have an emissions test soon that checks your drive readiness monitors, you could do a hard reset after replacement which will force the ECU to relearn the position.

 

Thanks for assisting!
I have to look into this as my contacts have said that the vehicle cannot learn the TPS position on its own which is why there is some clock adjustment of the sensor.

 

I couldn't find any procedure in IDS (V125) for the TPS, although there is one for the pedal position sensor.

My understanding is that the ECM will re-learn position after a hard reset, although that does beg the question why the TPS mounting flanges allow for some 'clocking'. Looking at some procedures for other cars, it may be to set the idle voltage to some specified value?

I'd be tempted to mark the position of the existing TPS, align the new to those markings, and see how it behaves. All the ones I've seen (admittedly, not many) appear to be set central to the slots.

If you discover this mysterious bench procedure, you can always apply it in situ with the TPS disconnected.

 

If I remember right when I replaced the TPS revs went up and down for a bit then settled. I guess this is the learning. I think after that I adjusted for the Goldilocks zone.

 

life is fill of compromises. You can have a car that has perfect drivability without setting the throttle position sensor perfectly.

in other words, you can do it on the car as previously suggested and end up with no bad side effects, and no loss of performance.

or not, I won’t lose sleep whatever you decide.

Z

 

Thank you @michaelh .

I have made a decision for now to only install the cable reel actuator and sensor and not disturb the TPS sensor. A couple of reasons, keeping one variable at a time one of them. My specialist from back East mentioned that he has seen an issue of wear at the butterfly shaft which allows not metered air. Recommends smoke testing. My fuel trims are great, so kind of rules that one out.

Planned to run the pedal position setting with my IDS, however it kept hanging at the pedal stop procedure. So, I aborted this for now.

The vehicle ran excellently, for a short while.

However, in the process I might have found a lingering problem which should be another thread. It is not due to this issue/replacement. Something was apparently ready to go, and another problem made its befuddling cause difficult to pin down.

I have an email query to the outfit which provided the rebuilt TPS and reel units and a TB rebuilder regarding this discussion. Anything which I learn will be shared.

Thanks for all of your help. Cheers.

 

This is what I purchased for those oddball screws...
Point Security Tamper Proof Driver Bit Set

 

Hi Cor,

The best info I could find in a quick search is in the Service Training Course 881 V6 / V8 Engine Management (attached). On page 44, it states that for the single-track AJ26 TPS, the voltage signal ranges from approximately 0.5 volts at idle to 4.75 volts at wide open throttle:




I do not see the voltage range for the AJ27, but this graph for the AJ27 is given on page 58, and it seems to show that the voltage at wide open throttle of the circuit 2 Hall Effect sensor should be in that same 4.75 volt range (perhaps a little higher for track 2):



Presumably, you could backprobe the TPS electrical connector, turn the ignition on, and measure the voltage output with the butterfly valve at the idle and WOT positions, and adjust the TPS so that the voltage at WOT is 4.75 volts.

I am also attaching the wiring schematics so you can identify the wires to backprobe.

Cheers,

Don

 

From the 2001 electrical guide:-

TPS 1 : 0.5 V = IDLE; 4.75 V = WOT
TPS 2 : 0.6 V = IDLE; 4.85 V = WOT

PPS 1 : 0.6 V = FOOT OFF; 3.8 V = PEDAL FULLY DEPRESSED
PPS 2 : 0.8 V = FOOT OFF; 2.4 V = PEDAL FULLY DEPRESSED

I think the only adjustment that is needed is to make sure the sensor can give the full range of values from fully closed to fully open with a margin for error on either side - no need to be super accurate, but you don't want either the min or max to be with the sensor wipers against the very end of the tracks. I'm guessing that on an earlier iteration of the hardware this did have to be set accurately on the bench, but at some point they realised the car could just learn the min and max. All IMHO of course.

 

Thank you everyone!

I am going to pause this and not change out the TPS for the moment as I have strong indications that it was not the problem.

Do not wish to introduce another variable until I sort out the other suspect(s).

Will revisit this at a later date and test the original in place to see how it corresponds to the values and procedures as given.

Once again, thank you for all of your kindness.

 

Partial UPDATE: This is somewhat related to my recent ECU thread.

More importantly, there was probably nothing wrong with the TB or any of its components.

A partially failing ignition coil can create the same effects which caused me to look here. The original problem was that idle would stumble for no apparent reason at random times, and then seem to fix itself for a while, often a long while.

When testing the vehicle after the installation of the throttle cable reel sensor/actuator, the coil finally failed totally. Moving the coil would move the reported failure.

These were new Beck/Arnley ignition coils, purchased and installed by me nine years ago, and this problem appeared on occasion shortly thereafter. No ECU code of course as it did not cross the threshold. Apparently the system does not log misfires below a certain threshold. I had two totally fail prior to now and assumed damage from when the harness was failing/shorted, since repaired.

Sadly, I have recommended this manufacturer here on occasion.

Was considering paying the full rent for a brand new set of Hitachi or Denso if I could find the latter. However, a breaker had a known good set of original Denso in his stock which I now have for installation.

My Jaguar technician friend thought that my minor evap issue was causing a temporary rich and thus the minor idle stumble. Then I moved on to the TB and potentially the TPS.

Seems that a partial misfire can cause this, and it can be caused by unreliable aftermarket coils.

More to follow as I sort out this annoyance.

Perhaps it IS fixed, finally?