Hi all, I see this has been a regular problem, but at risk of being boring......; I have a 1994 XJS 4.0 litre convertible, the idle is 1150 ! As I am in rural France, there is no-one that has the kit needed to adjust the idle, which can only be done with a diagnostic tool. Does anyone know of a tool that will do this for sure, hopefully not too expensive ! I hear there is one near Geneva, I am 700kms away in Le Mans !
I have tried and then contacted icarsoft, and they tell me the car is too old and they never did the software for the XJS nor the near identical X300 Any ideas ?

 

As far as I know, the idle can be adjusted at the throttle body.
Only need a wrench or nut driver.

 

No, sorry, had there been one, I would have adjusted it. The late XJS follows the X300 in respect of the injection, the idle can only be adjusted by a software programme This is why I am asking if anyone knows of a generic diagnostic tool that has this facility in the programme.

 

There is another way. You manually rotate the TPS.

This is what I suggest you do.

1. Remove the throttle body. It's held in by four 10mm bolts. There's no gasket and don't forget about the small coolant hoses that attach to the underside of the throttle body. (golf tees work perfectly to block the hose so coolant doesn't continue to flow out.)

2. Clean the throttle body, thoroughly, both sides of the butterfly.

3. Loosen the two screws that hold the TPS to the underside of the Throttle Body. See if there's enough play in the way it fits on to the throttle body, if there isn't, enlargen the holes that the screws use to keep it in place. Once all done, attach the TPS back to the throttle body where the screws are just tight enough that it requires a little bit of force by hand to rotate.

4. Put the throttle body back on the car. Remember, there are no gaskets between the intake and the throttle body, just metal on metal.

5. With the car running, you should be able to reach under the car and rotate the TPS to affect the idle. Once you have idle where it needs to be (700rpm warm engine) you can turn the car off and tighten the screws on the TPS. (Don't forget to add a little bit of coolant to replace what you lost)

Done.

 

Am I correct you are located in Le Mans France? I might know a company in Caen who still have the original diagnostic tool you need to do the reset. If you are interested send me a PM.

 

But, the reset procedure is for the AJ16 engine, as you say you have a 1994, it could be a AJ6 as well and than you should be able to adjust it yourself.

 

Gijzzy is correct. My email addresses AJ16 engines.

 

Believe me, having stripped the throttle body down to the last item to stop it from sticking slightly open, there is no manual adjustment at all in this body.
I will try the elongating holes and adjusting the TPS because that works on an AJ6. This is an AJ16

 

Another thing you can try (it's has been suggested elsewhere and has support from a blurb in the Jaguar document 801S), is to disconnect the battery, and after a moment, touch the ground & + side battery connectors together fully ensuring all residual power in all systems is discharged. On the AJ6 this definitely wipes the memory. On the AJ16 technically the eeprom is supposed to hold the adaptive values even with the battery disconnected, but it has been my experience that with the battery out for a sufficient period of time, the ECM does do a relearn process (certainly for shift points in sports mode... thus I assume....) This has the possibility to wipe all of the the little memorized trims and compensations in the ECU including causing the ECU to relearn idle - and thus the current TPS position (which is technically non-adjustable on the AJ16, but does have a little play). Never tried this type of reset myself, but I do have exp with the battery being out for an extended period of time.

~Paul K

 

I can assure you that touching positive and negative cables will not do a thing on the AJ16.

Been trying to squash this myth for years.

You can unplug the car for 10 years and the trim data will be exactly the same as it was before you unplugged it. You can cross wire, short circuit or do whatever else you want. Unless you have a device that can access that file, like a PDU or WDS, that data is not getting altered or deleted. Ever.

 

It works on an AJ16. Didn’t know it worked (for certain) on the AJ6, but I guess now I know?

Let us know how it turns out.

Keep in mind, when adjusting the TPS and tightening the screws when the correct rotation is found, you’ll be working in the blind. You won’t be able to see what you’re tightening, so make sure you have small enough tools to help you finish the job without being able to see it.

 

Although this topic is about a AJ16 engine, I had to share the TPS setup procedure on a AJ6 engine. Maybe it is helpful for somebody.
All you have to do is find a signal wire on the TPS or ECU to measure the voltage the TPS is sending to the ECU.
After the throttle setup, you can start the car to operating temperature and than adjust the RPM between 650 and 750.






Keep us updated Steve how you are doing with your car and your fix.

 

Damn AJ16

 

Wondering if you managed to get your idle as it should!?