I finally chased down an issue I believe I created. While discovering slack in my throttle cable, and my never ending desire to tinker, I believe I threw off the baseline TPS reading by slightly opening the butterfly a tad while trying to take the slack out of said cable.

I chased down various potential sources, until I finally realized what I may have done. See posts that lead me to my solution this afternoon
Jaguar TPS Tips
&
X300 TPS Installation, help...

I followed the method listed there. Mind you I have never worked with a digital multi-meter in any real capacity and got one a year ago.

Here you go, directions to fix or check up on your Jag's TPS sensor health and accuracy. A lot stems from the input this sensor gives the vehicle and when off, even the tiniest bit, it will affect 02 performance, fuel mileage, and most terribly transmission shifting issues.

STEPS
- Remove air elbow + rubber intake tube, MAF, etc.
- Remove throttle linkage, traction control linkage (if so equipped, mine is not), cruise control linkage
- Unplug EGR clip from upper right side of TB
- Using a vice grips, seal off the incoming coolant line to the bottom right of the TB and remove clamp from hose and remove
- Remove (4) 10mm bolts that hold the TB to the manifold. A 4"+ extension works well.
NOTE: no gasket needed, so you're not missing one if this is your first time.
-Remove EGR air hose from right side of TB
- Keep TPS plugged into vehicle
- Turn car to on but do not start
- Turn over the throttle body
- Insert a paper clip into the back of the wire of the MIDDLE of three wires connected to TPS
- Connect ground side to manifold.
- I used a metal clamp to hold both sides down so I could tinker with the sensor. I clamped the negative to the manifold driver's (US) left front and the positive to the paper clip.
- Loosen TPS screws. When loose, there is plenty of play to adjust to .6V at rest
- Adjust by turning the TPS gently to your desired .6V
-Uniformly tighten the two torx screws down, keeping constant .6V
- Double check voltage reading one more time.
- Remove paper clip
- Install in reverse order
-Go for a drive

The car has it's zip back! I think I have a Bank 2 sensor with some high voltage I need to replace, however this has fixed my frustrating issues from this post:

https://www.jaguarforums.com/forum/x...y-help-161798/

 

Yep, this is the technique the guys on V11 Moto Guzzi board have been doing since the early 2000s... twisting the TPS until the voltage reads correctly at butterfly close. In fact we had a guy that made a special harness that went in-line between the TPS and connector with flying leads so we could avoid using the "paperclips in the connector" which sometimes proved finicky.

I was thinking of doing the same when/if I put on my Maxbore throttle body to see if I can avoid having to get the dealer to do a throttle adaptation.


I've been meaning to look and see if the harness we made for the MG fits the Jaguar/Ford TPS but just haven't gotten around to it. I'll try to take a look and if it fits see if I can find the guy that used to make them.

So, BTW, did you grind out the TPS holes a bit to make them oval so you can twist it? The TPS on the MG has oval mounting holes to accommodate this technique, but the Jaguar/Ford TPS for our cars has round mounting holes that don't seem to provide room to move the TPS around. Your post in the other thread seemed to suggest you had enough wiggle room without having to grind open the holes, which would be good news.

Also can you confirm how your connected your pins to the back of the TPS connector, which pin was grounded and where the digital multi meter was connected to measure the .6 volt for this TPS?

It sounds like you were saying you only measured voltage between the middle pin and engine manifold(chassis ground) with the digital multi-meter in-between measuring the voltage, but wanted to verify.


Thanks for verifying this!

.

 

Good news, the wiggle room available is more than plenty, in fact, it took a few tries to learn the fine adjustment needed to get it at .6V EXACTLY and then tighten it down and not have it change a bit after being pulled in one direction or another. If you could use two hands you would tighten them both at the same time.

 

I am glad this worked for you, but it is not an accurate way to set the TPS.
Let me explain. The TPS gives a voltage for the particular position of the throttle butterfly. This procedure calibrates the close dposition to .6 volts, which is the nominal voltage for that position. However, the WDS or IDS software does a calibration where the ECU is taught the correct closed position voltage, then it remembers that voltage for the future. If the measured voltage was not .6 volts, then returning the TPS to .6 volts will not satisfy that particular ECU. Unfortunately, there is no good way to read what voltage has been taught for the closed position.
Again, I am glad this worked for you.

 

That's true for a TPS that is not set correctly (unless you want to fiddle and guess), but if you working from a known good TPS position, could you not measure the voltage before you made any adjustments?

For example, if you change throttle bodies, you could check the TPS voltage on the existing unit then adjust your other throttle body TPS to match voltage. This way you could swap back and forth without having to get IDS or a shop to do the adaptation.

.

 

Can you confirm/clarify exactly how you hooked up the pin(s), multimeter, etc?

.

 

While this did work, I find it prudent to take it back to my Jaguar guy and have him reset via IDS too. It's funny the first time he fixed it, the car down shifted better but then was herky jerky in 4th gear, then I went back and he did it again but the downshifting was herky jerky from 2-1.

The shifting is smooth as silk now however. I'll go tomorrow and have him reset once more knowing the TPS is in the right position when closed, which it was not...

 

AL, I literally took a paper clip, straightened out one end, inserted it between the insulation and the wire on the back of the clip of the middle wire, this one gave me the signal to measure. When done, I removed the paper clip! It was awesome, I then went and tested all of my coil packs and found three of them were out of range 2.5+ ohm and up. I felt like I belonged on the Big Bang Theory show last night with all of my new found technical know-how! Ha!

 

Absolutely, Al, but unfortunately most of us would not measure the voltage until we had a problem and then it is too late!

 

This is all very interesting as I intend to "look " at mine as my obd2 reader tells me I only have 53% throttle opening as far as the ECU is concerned .I am wondering what TP would show , on OBD , after adjusting using the above method ? SD96 If you have an OBD that tells you throttle opening I would like to know if it is not to much trouble .

 

John:
You should have much more at WOT- like 85% or so. Most likely, the throttle cable is stretched. It should be just loose from tension at idle.

 

Thanks Ross , that will be the first thing I check . My XJR is a 96 and I have owned it since 1998 and the reason I am looking at the TPS is that there was a recall to change the throttle body spring and I wonder whether the dealer replaced the spring and did not adjust the TPS , trac control and auto trans as directed by Jaguar , yes I am a pessimist when it comes to car repairs and always do my own. My plan is to do a 0 -60mph ( or similiar ) then adjust cable retest TPS ,road test , adjust TPS , road test , fit Andy bracket road test. I have heard some horror stories from an incorrectly adjusted TPS and would like to avoid spending hour after hour trying to get it right .

 

I recommend you do not touch the TPS adjustment unless you are sure you have a problem. Even if your 53% throttle reading is wrong, adjustment cannot fix a 30% or more error. Chwck where the throttle p[late is when the pedal is full depressed along with the ECU's measured position and the TPS voltage. Then do the same for idle, foot off pedal. Then see when the voltage begins to rise as you depress the pedal. I think yoiu will find the real situation pretty quickly by diagnosis if you resist the temptation to yank it all apart first!

 

Thanks Ross , I always believe in research before pulling things apart so I can resist the temptation . I will follow your recommendation's and see how it turns out .It could be a little while until I get around to it, working on my XJS at the moment .....John

 

Just wanted to let you know the technique I used when replacing my tps on my 1995 xj6. Maybe it will help someone. I simply made the mounting holes on the tps bigger to allow the sensor to be rotated . I hooked up my scan tool with live data and slowly moved the sensor until it read 0.00 on the throttle position. Then just tighten the screws down and boom no more shifting or high idle issues. Its a crude way to do it no doubt but it worked slick.

 

Hi jagxfsuperdude,

Welcome to the Jaguar Forums! It's great to have you with us!

Please visit the New Member Area - Intro a MUST and post a required introduction so we can learn something about you and your Jaguar and give you a proper welcome.

Cheers,

Don