Hi guys

Bought my XJR 1995 back in september. The idle was high at 1.200 rpm, but I read on several Jag sites that this is a known problem with the X300 and it can be solved.

On May 15 I drove my car to the mechanic as agreed upon a week earlier and let him take a look at it. I gave him some notes, including info on the throttle body spring recall (T493). I also said I considered it a TPS issue and asked them to reset or replace it. Wrote that on the note too. The rear shocks and the timing chain tensioner also had to be looked at.

The reason for me to suspect the TPS was an OBDII readout of 20% throttle when not touching the pedal and 80% at WOT. I have read that resetting the TPS is normal when the idle is high, but only jaguar diagnostics have access to that.

So today, after 10 days, I called asking for an update. It was almost finished by then. When I arrived we cranked the engine and it fired up straight away. The timing chain rattling as always, even though the tensioner was replaced today, and the idle was a steady 1.200 rpm

The TPS haven't been replaced and it haven't been reset either...

I was told the TPS on my car can't be reset in any way, shape or form. On earlier models the TPS could be rotated on it's own axis, but not anymore. The engine will adapt to the min and max throttle positions over time.

This is SO far from what I have read. My understanding is, that the TPS can't be adjusted physically, because it is now done on the diagnostics computer. You plug it in and 'teach' the ECU the min and max throttle positions. Am I way off?

A diagnostics on the TPS was performed and it came out ok. Then a kick down test, which it failed miserably. The pedal had to be pushed quite a bit before it registered. When the pedal hit and mashed the kick down switch, everything freaked out and the test failed, asking for a retry. No way to get through this test.

The mechanic then disconnected the battery for ten minutes, to do a reset. I said I doubted that would do anything, as I believe the settings are stored in nonvolatile memory, but...

And that was it. No more work could or would be done today. So, after 10 days of being without a car, I really felt dissapointed, but I wasn't going to let the car stay behind. The mechanic is a $50 taxi trip away in each direction, so I got in the car and drove home. After 100 meters or so, the gear shifting became very hard. Like being kicked in the back. Checked and sure enough, the transmission light was lit. I can't see that lamp during driving, as the steering wheel is in the way, so I have no idea when it turned on. This has happened once before and an OBD readout gave a P0123 error. That's 'The TPS is reporting too high a voltage'. That information was also on the notes I gave the mechanic, but apparently it was used for nothing. I pulled over and turned off the engine. Gave it a short rest and drove on. The shifting was somewhat better, but it occured at higher rpms than usually. This was persistant through a 10 miles drive home, in downtown traffic. When parking I noticed, that the idle was still at 1.200 rpm and the transmission light was back on...

This is my first Jaguar and it is turning out to be a real nightmare. The car was expensive due to local car taxes at $25.000, and now I am looking at a 12-14 hours mechanic bill at $126/hour for these 10 days and the only thing that was fixed, was the shocks. The timing chain still rattles, the idle is still high and now the transmission it totally out of whack too. I have only driven 1.000 miles since september and now, with the transmission failure, I can't even drive my family on summer vacation

Please, guys. I need HELP here!
Stefan

 

Just my humble opinion here, Stefan, but it ain't the car that's a nightmare, it's your mechanic.

 

your car has the potential to be one of the best cars you ever owned, don't give up you just need someone that understands your car... Most likely your idle is high because you either have a vacuum link at or before the throttle body, look very carefully and you most likely will find one. If this is not the cause you need to clean out your throttle body, not to bad of a job you just need to know what your doing. And yes your tps/ throttle potenentiometer can be reset. you would need a shop with the right setup to communicate with your cars computer. Remember, you should never turn your ignition on if you have tps disconnected from your car when you are cleaning your throttle body, this will cause the tps to relearn a different setting for closed throttle and then your idle will be off for sure. The problem is not as big as you think..

 

sorry meant to say vacuum leek.

 

Thanks for the feedback.

The throttle body was cleaned by the mechanic. Not very dirty, he said. No words on vacuum leaks, so I guess there was none.

I was expecting a replaced TPS, or at least that it was checked thoroughly, as everything pointed in that direction and the throttle body was off anyway. Now all the work will have to be done once again, at the hourly rate described above, and this is killing my wallet. I'm not made of money and my health is not good enough to tackle the job myself.

The mechanic is supposed to have all the right Jaguar gear to do this job, but somehow the issue is exactly the same as it was before his 10+ hours of work. So it looks like I will have to do the troubleshooting if this is ever gonna be fixed and I can't do that without help. That's why I am here. Looking for answers that the mechanic have missed.

 

The XJR throttle body is a terrible job to remove. I have a similar concern with my naturally aspirated AJ16 but have been lazy about cleaning the throttle body (which is easy as can be without a supercharger in the way) I don't imagine yours was cleaned.

I do agree that your mechanic needs replacing. These cars are very particular. Hopefully there is a better mechanic on Jags nearer to you.

 

Well, there aren't. Due to 180% car taxes in my country, Jaguars and other top end cars are extremely rare. Only a handful of jag mechanics in the whole country.

The more I think about it, the harder it is for me to understand why the TPS wasn't replaced. I even ASKED for it. Everything, literally EVERYTHING points in that direction. Why else would the idle be high, the kick down test fail, throttle indicator be min 20% and max 80% and the P0123 error pop up? Even a flashing 'Error here' neon sign pointing at the TPS couldn't be a clearer indicator imho. Or?

 

I have the 95xjr and it does not take 10hrs of work to remove and clean the throttle body, its some work but no way 10hrs.. I have done this in less than 5 hrs. The potentiometer/tps can be replaced, just bolt right on the way you take it off. with special care that the throttle remains closed when the potentiometer is bolted on. If you need to replace the potentiometer i have found a great replacement that will not break your wallet as the original is very costly. I have attached a pic and ford part number of a replacement that can be had for 30 or 40 American on ebay brand new. take a look at your orginal part and it has ford stamped right on it and it looks exactly like the one in the pic part number 90TF9B989 . compare it to the pic of our original tps, they are the same, our tps is part number 70418a. I would say take a look at idle speed control valve but I dont think that would cause your idle to go as high as you say, i only say this out of experience. I really think its a vacuum leak. Hey, have your tried to adjust your throttle cable? that can also be the culprit, you can do this adjustment in 2 minutes.

 

dont be fooled you can change the tps/potentiometer without taking your car apart. this could be done from underneath, remove the oil filter and maybe the tubing to the throttle body and you have the room you need to do the job. takes 10-15 min tops, I have done this. dont be taken advantage of the xjr6 is a great car it does work and it could make you very happy.

 

Let's say I have the TPS swapped. How will the ECU know the TPS is replaced and adapt? The mechanic can't find anything in the diags computer to do that?

Don't know how to adjust the throttle cable, but I think the mechanic will have done that, after working on the throttle body?

So much guessing involved, because my back is too messed up to do the work myself and I have no idea what the mechanic do and didn't do :-/

Oh, and jeremiahjaguar, your info that the TPS can be replaced without removing everything, gives me a new small hope.

 

YES IT CAN !

You need to make an appointment with your local Jaguar dealer and request them to reorient the tps with the on board computer.
Had same problems with my97 a while back,cost about $80.and
about 1.2 hours and can be done on an hot engine.Well worth it,
Saved me alot of shooting in the dark on parts replacements.

Eddie T.

 

Eddie T,
We are talking about a diagnostics computer like WDS here, right? Not physical adjustment?

Update:
Had the OBDII reader connected and found these errors. Related to the total misinformation sent by the TPS?

P0730 (Incorrect Gear Ratio?)
P1775 (Transmission System MIL Fault?)

 

p1775 is the code for the TCM either it is bad or the connections to the TCM are dirty or faulty. dont know about the other code. Hate to see a good jag gone bad at the hands of a incompetent mechanic. believe it or not your xjr is one hell of a car, just needs a real jag mechanic. When you sort out the bugs I can tell you how to give the jag some claws on the road with small inexpensive upgrades...

 

Don't think I have the money for this car Think I am out about $6-8.000 already since september for driving 1.000 miles all in all and still the same issues. Gonna loose a lot of cash if I let it go in this condition, but when the pocket is running empty, not much else to do. Gonna give it a another go first, though, but it has to be at low cost. Not gonna throw good money after bad...

Can I buy a XJ6 X300 and use it in my XJR? There are several on eBay, but they all have different numbers. Have written a pro seller and asked for help, but if anyone have the information, please let me know.

Oh, btw, the mechanic was fiddling with the gear selector. Had a lot of problems trying to get it into Neutral. The lamp wouldn't light up. Yet another issue I have to fix, or can this be the reason for the TCM code?

 

you said that you once disconnected the battery to reset the computer, how long did you leave it disconnected? I once had the throttle body off and turned the ignition on to put up the windows as it started raining. I was afraid that I would have to take my car in to the dealer to reset my tps as I was sure that when I turned the ignition on that the computer would relearn a different setting for closed throttle. However, i decided to disconnect the battery and try to reset the computer.. It rained for days and the battery remained disconnected for a full three days after I put everything together it started right up. I can tell that the car was adjusting to each cat as idle stumbled a few times but after it warmed up all was well. disconnect your battery hit the horn to get rid of any charge in the system and let it sit for a few days. worked once for me, maybe it will help..

 

It was only disconnected for ten minutes and it was done by the mechanic, not me. I believe the data is stored in nonvolatile memory, much like the harddisk on your pc and not ram, meaning it should be kept for an infinite amount of time. Come to think of it, my battery died few weeks after buying the car and it took days before I replaced it. Changed nothing on my high idle :-(

 

Found this item on eBay. Have you actually used it yourself, or does it just seem to fit? Wondering if the ohm resistance is the same...?

 

both petentiometers are made by ford and have the same ohm resistance, they look exactly the same size, design and the connection plugs are the same. I have never used it personally but it will be my first choice as soon as i need one. What you should do before you change the pontentiometer is have a jaguar dealer/shop/mechanic orient your computer to your pontentiometer, only 80 bucks and it will save you headaches.. You may not need to buy a new one.

 

jeremiah -
Why do you suggest orienting the TPS BEFORE replacement? Are you thinking that it might only need adjustment? I would guess from the description that the TPS is bad and should be replaced. '

The TPS is calibrated by running the TPS adaption on either WDS or IDS. If the mechanic doesn't know that, you need to find a new mechanic.

 

Ordered an original TPS. Will not risk bad result and then still not know if the TPS actually is ok. Will update here when it is installed.