High rpm on 96 new XJS 4.0

Four days old, ran beautifully, now rpm ar 2200. Not a linkage issue. Local mechanic said it might be TPS. Now Check Engine light came on and Check Handbrake warning light as well, which was not engaged. Am in Port Angeles WA, very disappointing first few days with issues. Drove 5 hrs a few days ago with no problems after purchase. Any advice appreciated, or where to buy a TPS. First post-how to include pix? Thanks, Stuart 707 799-1927

Welcome to the forums.
Not sure if this would be a test but have you tried disconnecting the TPS and seeing if the RPM is still high, personally I can’t see how it can cause a high rpm situation, I would check for an air leak around the inlet manifold.
Check the brake fluid level, that may be low causing the light to come on.
Invest in a code reader to find out what’s causing the CEL, or if you can get the car to a FLAPS they sometimes have readers and will tell you what codes are stored.
I had a check engine light on my ‘06 X type yesterday and my iCar 930i read a misfire on cyl 6, probably due to the water leak I discovered coming from the small crack in the header tank. The code reader cleared the code as it had by then stopped misfiring.
To post a picture use the up arrow bottom right of the window you type in, as a new user you will be limited to 1 picture per post until you have a few more interactions with the forums.
You can add a flag to your avatar and I would suggest keeping personal contact info off your posts.

Thank you for all the useful information!!

TPS can absolutely cause a high RPM, but it’s not common. Replacing it will probably stain your seats as it is a $400+ part with no known alternatives.

  1. Check for a vacuum leak. Somewhere between the MAF and the intake, there could be a gap. Be 100% certain there isn’t. One way to do this would be to Saran Wrap one end of the MAF, reinstall everything, then disconnect the hose at the intake elbow and blow into it. It would be better if you could blow smoke into it. If you can’t continue to blow air in through the hose (remember blow into the elbow, then when you’re satisfied with that, blow the other way towards the engine), then perhaps it’s not a vacuum leak.

  2. While the engine is running…hot, or at least fully warmed up so that the car is in closed loop, unplug the TPS. Yes, I know, it’s hot and you’ll have to snake your hand around an engine to get to the underside of the throttle body to get to the plug. Count to 10, then plug it back in. Anything change? OK, on to the next one.

  3. With the engine still running, see if you can budge that TPS. If you can, you’ll notice a change in RPM, faster or slower. If you can’t, there will be no response. Move on.

  4. You may simply need a TPS reset. Unfortunately, that requires a device with Jaguar specific software. Dealers should have it, and charge you 1 hour of labor. Other jag specific, or maybe other garages could have a device that could do it as well. This should almost certainly fix this issue.

Here’s the kicker. Replacing the TPS will almost certainly require the TPS reset I mentioned in #4, so buying a new TPS will not solve your problem.

  1. When you get home, you may need to clean the throttle body. It is easily removed with 4 10mm bolts, and don’t forget two golf tees to plug up the coolant hoses underneath! You will find a fantastic amount of sludge and grime on both sides of that butterfly. Don’t try to just clean it from the outside, you will need to remove it from the car. Have a full can of carb cleaner ready, with a rag.

Please share the engine code with us. Please tell me you’ve invested in a cheap OBD2 reader? I would recommend buying the one Robin mentioned, because it does pull unique jaguar ABS and Transmission codes!

Also, which light do you think is the Check Handbrake light? There isn’t one, so I’m curious to see what you have on? I’m hoping you know how to disengage the parking brake. Whether it’s engaged or off, it the parking brake handle always lays flat.

Thanks for the extensive list of considerations and solutions! I am not a mechanic, bought the car because the service dept of the dealership of the high end cars had gone through it. Drove it home 5 hrs without issues, now can’t drive it. In two days taking it to a mechanic at a dealership who works on foreign cars and I will give him your notes. They will get the air conditioning working at seller’s expense, and now I am going to include the new things. I do not have an OBD2 reader, will see how to get one.
The Park Brake light now stays on, also the red Check engine. I did disengage the parking brake while driving, and now it does not stay in the up position, though I did raise the convertible top while holding it up, so I will have them check this as well. Thanks!

The parking brake isn’t broken. It’s supposed to lie flat whether it is engaged or not. By feel, you should be able to tell if it’s engaged. It it raises freely, it’s engaged. Raise it as far as she’ll go, press the button and hold that button until it’s back down to disengage. That’s likely why the BRAKE light is on.

Check Engine should be amber no? (I could be wrong) You’ll want the iCarsoft i930. eBay has one for $100. You can buy one for much less, but you won’t get the ability to read Airbag and Transmission codes. It is likely worth it.

If you can find a Mongoose, it would allow you to reset your own TPS. That would certainly be worth it.

Can I reply via email? Will try
Check Engine light is orange/yellow
Park Brake is red and lit
I pull up the handle and it does not stay
I push the button it does not stay
There is no ratchets or resistance while pulling up the brake
Seems it would click in the up position and release pushing the button?
I do not have the owners manual and only had the car 5 days
The top did come up today while I held the parking brake in the up position
Thanks

Stuart.

I keep trying to explain to you, it does not stay. It will never stay. It isn’t supposed to stay. It will always lay flat, engaged or not.

Since it’s not ratcheting when you are pulling up, the brake is engaged. That is why the red brake light is on.

To disengage, raise it, hold the button down and raise it further, still holding the button, and then let it down, while still holding down the button. Once the red brake light is off, you can release the button and let go.

Stuart. If you hear no ratcheting, it is because the parking brake is set. The handle will have no resistance and will come rest at the bottom position. (If you have a LHD car you will appreciate this feature if getting in or out of car with parking brake set). To release pull up on handle until you feel resistance and then push in the nuttiness and hold it in, pull a little higher and then lower the handle while keeping the button pushed in.
As I understand convertibles (I don’t own one) the top will only actuate while parking brake is set. One of the convertible guys will say something .

It is true. For top to work, car must be in Park and parking brake must be engaged (red brake light on).

I happen to have a 1996 XJS Convertible as well.

Stuart, there is an internal email system within J-L, touch the posters avatar and a blue message icon will be there, when you send an internal email a green envelope will appear at the top right of the recipients page, I hope this helps.

YES!!! SUCCESS!!! The so much. Learning. With help.

VK
BRILLIANT! Did not understand, now I do, many thanks!!! If I reply by email, could you please let me know it has been received? And if an email reply, is it to you only or the group? Once again, much appreciation!

OK, crawl, walk, run. Got the parking brake issue resolved with your help, many thx! Yes, with LHD it would certainly be awkward to do Yoga to get over the engaged upright parking brake. Tomorrow, leaving the car for AC which seller is going to cover, and also the high rpm and Check Engine light.
Will keep posting developments. Now, six days since purchase and what a delight when car was driving well, also wife loves it. Even more than the 57 Tbird I sold. Thanks, all!

I will confirm if I receive an email from you.

VK, car dropped off and will report findings. Meanwhile, looking forward to the driving, and maybe new wheels. Current ones are fine ,red, but those on blue car, not mine, I like better

The ones you have were standard for the 4.0 1996 model year.

The ones you like are for the v12

There’s also a 5spoke found on the 95s that I prefer most

Do the V12 wheels fit on a 96? Car in shop so can’t read tire info. Pix of your 5 spoke 95? Standard 96 pictured wheels fine, as I wrote, but some others would be the cat’s meow…if expense tolerable. Thanks.

I have the 20 spoke diamond turned on my 95 v12 coupe
I like them

Yes.
Like them better too.