In my continuing quest for an off-the-line performance improvement, I'm going back to square one, starting with the engine set-up procedure.

At the same time, I thought I might as well replace the throttle pot (ordered it 6 months ago, but never got around to it).

Not sure this is "stock" or not, but the shaft of mine is welded to the plate that has the two screws in it (see photos).

I can grind the weld off, but not sure if I'm creating a worse problem by doing so (having no idea why it would have been welded in the first place).

Thanks,

John
1987 XJ-S V12

 

It is welded so that the spindle underneath turns when the capstan turns! All you have to do is remove the three screws that hold the black TPS and replace that with another (now available this "Bournes" model, did not used to be) obtainable from David Manners if not all the other specialists.
The TPS in the background does not seem to be an OEM piece. IF you want to jury-rig it, then you need to remove the spindle (and its welded plate) and find a way of:

• connecting the spindle to the TPS axle, and
• fixing the new TPS body to the capstan chassis so that it can be easily adjusted.

Greg

 

Hi Greg,

I did remove the three screws...the throttle pot won't budge.

I didn't try prying it, but if it's welded at the factory I guess I'll put some leverage on it.

Thanks!

John

 

It is not welded. The TPS is just a push fit into the spindle shaft; remove the three screws and just pry it off carefully.

 

Thanks for that Greg.

Just took a small pry with a screwdriver to pop it out.

I am going to replace it with the Hall Effect sensor shown in the earlier photo, mainly because it's much cheaper than the Jag part and it has the same electrical characteristics with the same 90 degree rotation.

Attached is a photo of the inside of the thing for those interested.

Thanks,

John

 

Good job. I would be very interested to see photos of how you fix up the new sensor.

 

Very good, will post them tomorrow. Working on finishing it up now.

Cheers,

John

 

Got the Hall Effect Sensor (HES) TPS installed, works as expected.

I cut the wiring harness off the original TPS and pitched the rest of it. Soldered some extension wires onto the harness/HES to make it a bit easier to get it in and out.

Used a longer bolt, same diameter as the original spindle shaft (or whatever it's called), and welded the bolt to some plate steel cut to the same diameter as the plate on the original. This was necessary because I had to have some thread sticking out to attach a nut, and the original shaft isn't threaded and doesn't extend beyond the bottom plate of the TPS assembly.

Welded a sleeve (that fits onto the HES shaft) to a nut that screws onto the bolt. Drilled and tapped locking screw holes in each. Took a piece of sheet aluminum and formed a bracket to hold the TPS. Assembled it all, put a meter on the HES and turned to top of the spindle until I got to the required voltage, then put an index mark on the shaft, drilled the two holes that hold the plate to the TPS body, tightened down the locking screws and put it back in the car.

If you do this, make sure you have the spacer that holds the TPS assembly on your workbench so you can judge if the thing will fit back into place.

The one unknown is how long the HES will last in that environment. It's rated by Honeywell to 85 degrees C. Hopefully this is a conservative rating. Time will tell.

Thanks,

John