My XJS V12 (a 1986 engine) needs a new TPS.

There seems to be two options:

1) Go with the old-type, original TPS (mounting flanges at 120 degrees apart) if I can find one (I think jagbits has it)

2) Go with the new-type, sealed, red-colored unit with an "adaptor kit" that allows it to mate with the old throttle body. (XKs sells this.)

Would someone with experience please let me know if there is any rationale in going with the old original type, or the new retrofit?

If the new one is arguably better, then I'll go with that. But it looks a lot smaller, although sealed, and rather cheesy. The older one is like an industrial-strength rheostat-looking thing.

Thanks for any advice concerning this quandary!

 

The original was the "Bournes" TPS. As far as I know all the replacements for it are "brand x". The one I bought only lasted 6 months...maybe I just got a dud. I think later red type is higher grade.

If you like little projects and have 2-3 hours to do some minor fitting work, you can use a $30 TPS from a '1992 Ford Mustang 4 cyl. If that interests you I send along a few details


RTLL

 

Doug,
It seems this could possible be the perfect solution for my problem as I really can't shell out the +/-$300 for a Jag tps. How much "fitting work" are we talking here. Could you share the details on that?

 

A J-L posting of mine from several years ago. If more details are needed, give a shout. I have notes written down somewhere...






I used a TPS from a 1993 4-cyl Mustang, AC Delco part number 213-848

It is compact and rotates in the right direction with a 270º swing.

The drive spindle on the Ford TPS is the "round with two slots" type as
opposed to the Jaguar "round with one flat side" type (as you'd see on a
radio knob, for instance).

Using a sharp utility knife I cut the plastic drive piece off of the Bournes
TPS, leaving me, essentially, with a 3/4" long, hard plastic black tube
which engages the drive on the Jag throttle turntable.

It was then a simple matter to notch the other end to engage the Ford TPS
slotted drive. A couple of trial fits and adjustments for length and the
Ford TPS fit up against the bottom of the throttle turntable almost like it
was "Bourne" there, even has a raised, round area to correspond to a round,
recessed area of the turntable.

When cutting the slots you'll want to observe and be aware of the final
orientation of the TPS....you'll see what I mean.

The Ford TPS has a range of .38 to 4.80 volts. The .38 is a whisker higher
than the ideal closed throttle setting (on an HE) of .32-.36 volts
(depending who you are talking to) but, as far as driving the car goes, it
is great. Whether or not this difference is enough to be worrisome during an
emissions test, I can't say.

I have no detonation, pinging, or outward sign of lean running at WOT,
either, which was a concern since 5.0 volts was not obtainable. If I should
be worried here, somebody please tell me.

Since the "at rest" voltage was .38 there was no point in allowing for
adjustment....it can't go lower and you wouldn't want it any higher....so I
simply screwed it onto the underside of the turntable as is, in a fixed
mounting.

I Googled "Ford TPS" and easily found which pins on the Ford connector would
correspond to the Jaguar wiring. I cut the harness off the Bournes unit and
using (smaller than usual) spade connectors attached it to the Ford TPS. I
used black RTV silicone to fill and seal the rather large connector cavity.
The installation came off nicely, all-in-all. Of course, being hidden,
nobody will ever know :-(





Cheers
DD

 

Thanks for the quick reply. This seems simple enough and it sure beats a few hundred bucks. I'm not too concerned about exact readings; at this point anything is better than it's current running condition.

 

Well I've got the mustang tps fitted in. Drastic improvement. Throttle response is what I notice the most. No test drives though, it's still not registered yet. Plus I have the exhaust to put back together still.

On initial start-up is there some type of warmup cycle or any reason it would be idling at 2000 rpm? I haven't let it run long enough yet to see if it will drop to normal idle after a while.

 

Nice Mythbusters quote.

 

That is the cold start function. After it warms up it should settle in to around 600-750 rpm. And radarwhiz, how do you insert the quote and profile picture? :-)

 

Bottom right of each post are a few buttons, "quote" is one of them. That brings up the reply window and in the text box will be the post you're quoting. You can edit the text between the quote brackets however you want. Just leave the code inside the brackets there.

Across the top of any page the first tab on the left is "UserCP". That's "user control panel" where you can edit any bit of your profile. The second option there is to edit your profile picture. You can upload one from your own computer or paste one from the www.

 

BUMP for pics.

 

Here's the underside of the throttle turntable with the mustang TPS rigged up. You can see the pattern of where the stock one was and where the new mounting holes are. I just cut the harness off the old TPS and spliced it into to mustang one.

 

did mine up exactly the same. glad to see it.

 

bump. my TPS is running .47v at idle position and 4.7v at its maximum travel. my XJS throttle travel will only open it up to about 4.1v with my kickdown screw turned out all the way.

im reading .58 kohms at idle at the yellow post and wiper and 3.83 kohms at idle at the green post and wiper.

 

I had to bump such nice thread.
So, I got that Ford Mustang 4 cyl TPS today for $25, some Advance Auto Parts brand, says made in USA.
After soldering wires as shown on picture above, I realized that this TPS has round sleeve on its face that fits perfectly snug into Jaguar throttle plate.
In idle position that TPS was showing .52V, so something had to be done.
Here is what I did, on pictures.
I cut top of the TPS open very carefully with air blade, then removed back cover and ground off about .5mm in one by one tiny slices with sharp razor blade. After measuring few times, I got down to nearly perfect .32v. After that I sealed back cover again, with soldering iron melting and liquid electric tape.

P.S. Now that I think about it, I should have ground the other side as well, to get 5.0v, but it is too late, it is sealed and I am stuck with 4.65v.
P.P.S Just put the whole thing together and car runs fantastic, a lot more torque and wheel spin in second gear. Reading on hot motor is .34...

 

I thought I'd add to this old thread as I used it for some great reference. I ran into the same dreaded black TPS failure as many. I did contemplate the use of the ford TPS as many here have used. In the end I decided to use a Red Jag TPS, but needed to adapt it. I suppose I could have just bought the adaptor or purchased a unit on ebay, but my fabrication mindset over ruled that logical thought. Attached are some pictures of how I used the old black TPS as a mounting adaptor for the Red unit. By using the old unit with some creative modification, a quick spin on the lathe to reduce the overall height of the filled black unit and some high temp JB weld I was able to create an adaptor that uses the factory mount and pilot to ensure that the red unit was properly aligned. A simple saw cut in the throttle shaft perpendicular to the original flat on the "D" drive and as deep as the "D" flat is cut and away we go. One small advantage is now I have more adjustment as both the black and red units are slotted. The JB weld is good for 500F so we should be good there. I also heated up some small metal nails and pushed them through the sides of the old black unit to create "rebar" inside the JB weld for a little extra grip. Hope this helps someone out....

 

I about to do this with a Ford one (which are getting harder to find as well)

Did the wiring for the Ford and the jag stock wiring match up in coloring?

 

You can also save a deal of effort and buy a new Bournes type one from Manners.

 

Still would cost me a 100 dollars after exchange and shipping

The mustang one was 20 bucks.

 

Not likely....but I actually don't know what colors Ford used.

I have notes on which wires go where....but it'll be a few days before I can put my hands on that info. I might've posted the info here or on J-L years ago so an archives search might be in order.

Cheers
DD

 

Indeed, but is there any recent info/feedback on durability/lifespan?

My experience with the Bournes replacements isn't good....but it was years and years ago that I had one.

Cheers
DD