Hello ,
I recently have come to own a 1994 XJS convertible with a 4.0 L engine. Not new cars but new to Jaguars . I will be asking lots of questions after searching though posts of course . The car is a low miles California car in very good shape , It was my uncles and he owned it for more then 20 years. Now to the issues and questions. I will try to ask one question per topic which I think would be proper .
The car was shifting hard from 1 to 2 so my uncle took it to a local shop. It was diagnosed with a TPS error code . He deiced to not have it repaired and gave me the car. Taking the word of the shop I have set about changing the TPS. After removing the air mass sensor I noticed the screen or element on one end is detached by about 1/3rd the way around . I assume the AMS will need to repaired or replaced . Q1 ,can it be repaired? or is replacing the only option. Q2 , would this damaged AMS cause the hard shifts? Ok I asked two question but they concern the same part.
BRUCE

 

Welcome to the world of old Jaguars! Yes, the TPS is most likely the source of hard shifting, a common issue. Before replacing it, try this "quick fix" if you find the TPS is covered with oil/grease. Spray it completely with a parts cleaner. I do this once a year as a preemptive maintenance thing. Works every time. Also, unplug the harness and spray the contacts with an electrical cleaner. As a personal thing, I also have put a length of ribbed, plastic wire sleeve from the plug to the TPS to keep the wiring protected from oil/grease contamination. If all that fails, there is a detailed "shade tree" remedy to drill small holes in the bottom of the TPS to allow oil to drip out the case in due course. You'll find several discussions on TPS remedies.
Good Luck!
Dave in AZ

 

Since its a 1994, Ill save you a bunch of money. You dont need an new TPS, drill two small holes into the bottom of the housing, careful not to drill past the plastic housing. Then insert the straw of an electronic cleaner spray, in one of the holes and spray it til the fluid comes out nice and clear via the other hole. Now you have a escape route for any oil and residue to drip out of in the near future. No need to remove the TPS and deal with recalibration. A new TPS will result in the same problem if those two holes are not there, so dont forget to add them if you already got set on getting a new TPS. You dont need a new one. Its way easier if you do this with the car on a lift. I hate it when mechanics dont suggest the real fix just to make more money.

 

Just make sure the TPS does not look like JLM12074

If it does, there's no need to drill any holes anywhere. Taking the throttle body off and giving it a thorough cleaning would be a good, and very low cost start.

 

youre absolutely right. Those dont need speed holes!

 

Bruce,

If it's a 94 car with low miles, there's a possibility that it's still running with the original 28-year old auto transmission fluid. A lot of change problems can be resolved on these ZF 4-speed boxes just with a fluid and filter change.

Change the fluid and filter unless you have proof that it's been done in the last year. Fluid is cheap, gearboxes are expensive.

Cheers

Paul

 

Thanks for all the good tips.
My uncle had a collection of four XJS's and is a excellent mechanic But he is up there in age and didnt drive this last one more then 1000 miles in the last 5 years .All the fluids look pretty good. I Intend on doing all required maintenance but I'm up against a clock as far the weather around here goes.
I now have the throttle body off and the TPS is the red one if that helps. The ford mustang TPS looks nothing like the jaguar one . I assume I will need to make a mounting plate if i choose to go ahead with the ford one. However the Ford TPS has only three pins and the Jag part has 6 . so I assume the Ford part wont work . I need to reread the post on that again. Maybe I misread I would like to know where to drill the holes in the original TPS. Getting to the throttle body wasn't bad at all . If I need to do it twice that would suck but overall not to bad.

 

You drill two small snake bite holes at the lowest point of the TPS, So orient the TB in the mounted position and drill two snake bites on the lowest horizontal panel of the plastic housing. Insert the straw and spray inside. Once the TB is remounted, oil and soot should drip down those snake bites instead of accumulating inside the TPS housing.





drill into the plate that faces toward the ground.


Dont drill too far in. Here is a pic of the TPS with no lower plate. So that you can drill away from any of the guts inside.

 

Thanks for the information on the holes . I will drill them today and clean out the TPS and reinstall on the car. Which leads to the next question. There is no gasket on the throttle body to engine connection and no evidence of RTV sealer that I can see . Should I use a light smear of something like Ultra black RTV ? seams like there should be something there to seal it.

BRUCE

 

Listen to Brewtech. You do not have the JLM12074 type of TPS. There is not alternate TPS for these cars. Many have searched....

 

I have drilled the holes this morning and cleaned out the TPS with contact cleaner . The cleaner ran out brown for a bit and then went clear. I will be reinstalling the throttle body and other bits today. The Ford unit conversion looks to be for the V12 not the i6 like I have . Jaguar sure is proud of that TPS , 300 bucks, wow. I will report on how it goes.
BRUCE

 

After reinstalling the throttle body and related parts the car started right up ,no codes ,no transmission light , idles perfect . took it for a 20 mile drive and it shifts like butter. So a big thank you for all of the advice from the forum members. Hopefully I will be able help someone in the future . Again thank you .
Bruce

 

So... after another 20 miles or so to the transmission warning light came back on and the 1 to 2 shift is hard again. I will try cleaning it out again after the engine cools down, but am I heading for needing a new TPS now? I thought I had it pretty darn clean before.

 

Yes, clean it one more time, and obviously make sure you do have atf in the transmission. The transmission is essentially going into limp mode due to electronic info at the TB not being transmitted or received. You can clear the codes by disconnecting the battery. It took me a couple of tries. I even replaced the transmission module relay too, JIC, but I started backwards and eventually ended at the TPS, which was my problem.

 

Brewtech ,thank you for continuing to answer my questions . yesterday I disconnected the battery and was able ,not so easily, get the can of cleaner down into the engine bay and get the red tube up into the TPS. That cleared the issue again. I then took it for a drive of about 10 miles all was good until the the last 1/4 mile , The transmission light came on and the hard shift. I also had the E brake light stay on while driving which then would light up the bulb warning lamp when I stepped on the brake. while sorting that issue the trans light went out. I will drive it some more today and see what happens. I had wanted to drive it to my winter storage location next weekend . I will drive it next week to work every day to put it to test a bit ,

 

i came up with a idea for spraying the cleaner into the pre drilled holes in the TPS. Maybe it's be thought of before but I pulled the copper out of 12 inch piece of wire and super glued the remaining "tube" onto the nozzle of the spray cleaner. Now I can hold the can upright while I put the tube into one of the holes. Right no warning light or issues but will be driving it around a bit today. we will see.....

Bruce.