I have a 96 XJS 4.0 that just started having a high idle. At start it idles around 1500 rpm, when driving you can take your foot of and maintain 40-50 mph. I have cleaned the throttle body,changed the TPS and IAV. I think the seed sensor is ok as the rpm comes down in drive when I stop (800 rpm). The only way I have been able to control it is by disconecting the IAV, and manualy setting the length of the IAV piston. Any help would be much appreciated.




Craig.

 

Did you set up the ECU after changing the TPS or did you loosen the hole of the TPS so you can adjust the position of it?
You need to do either of above, or ECU can't figure out the position of the TPS and raise up the idle.
You have to take your car to the dealer to set up the ECU, for you will need PDU(portable diagnosis unit) to set it up.

 

No, I have not reset the ECU and I am unable to adjust the TPS as it is a fixed position on the facelift model. So, I guess that leaves a trip to the dealer. Is there a another way to reset the ECU?


Thanks,


Craig.

 

reset fueling parameters that is done with a PDU, which is rare.

For $150 I bought a JLR tool that allows me to reset the TPS. Might be worthwhile for you to purchase one too. It was on eBay.

Jaguar Land Rover Diagnostics equipment | British Diagnostics

It's a bit flakey, but will work. It does not reset parameters which was what I needed to have done when I first bought the car.

Does the idle remain high in drive and park?

 

This happened to me once after a non Jag guy worked on it... turned out the throttle pedestal needed adjusting. Not sure if the I6 has a similar arrangement.

 

If you don't like to go to a dealer, you can drill and slotting the mounting holes for the TPS to be adjusted.
I know it is an expensive part and you don't want to fail, the safest ways is to go to dealer. once you have set it up you don't have to go there for another 10 years or more.

But JLR tool, which Vee referring seems attractive. $150 is a good offer, I think.

 

Wow. That's what someone must have done to my old TPS. I thought it had been worn down or something...

Good to know.

 

Yes, I have seen them on ebay. I sent them an email asking if it work for a 96XJS and got no reply. Looks like it would work for the TPS then.


Thanks.

 

In drive with foot on brake around 800, Nuertral and Park 1500.

 

You may have developed a vacuum leak. Check all the possible places, either by using a propane torch (not lit, but emitting gas) or carb cleaner.

 

Then you're probably experiencing a hard shift when going into Drive from Park or Neutral...I had the same exact issue.

I was charged $150 to hook it up to their PDU to reset the adaptations. Looks like a trip to the dealer might be in order....

 

I just bought a Genrad 3500 of ebay which should be here Thursday, I think it has only Ford discs with it. I will need to find the Jaguar discs! If not I guess I'll have to go to the dealer. It is definitely hard on the brakes and gearbox.

 

I installed an IAC valve and a CPS on my '96 and have had a perfect 600 rpm idle for about a year. Today it started idling at 800 rpm in drive. I wish things would stay put on these cars. I will be watching to see if you find a fix.

RagJag

 

Could indeed be a vacuum leak. Have you checked your throttle pedestal?

 

On the AJ16, vacuum leak seldom occurs. Even if it does, it doesn't cause high idle like V12s, for the fuel isn't rich enough to do that. When vacuum leak occurs the idle won't be stable.

At least a TPS is replaced this time, resetting the ECU is the first thing to do.

 

Thanks, I did not think of using a propane torch.
I tried and all is good no leaks.


Craig

 

My 96 xjs suffered with same problem. Mines fitted with the XJR6 motor. Being in the trade, i have snap on Solus scan tool. it wouldnt go in via Jaguar, but going in via EOBD, it let me reset the emission data which sorted my high idle. So if you have removed your throttle body to clean/renew componants. try find a garage with a decent diagnostic tool and ask them to reset emission data through eobd if unable to go in through normal make and model.

 

Today I reset the TPS with a genrad 3500 that I had bought from ebay, and help from xjrguy and motorcarman. I also pulled the DTC's and found a problem with the secondary airflow. The secodary airflow pump electrical connector had come disconected!


Now, idle is smooth and all is good...


Thanks for everyones input, much appreciated.


Craig.

 

Hello! New member, Patrick in SanDiego, 1996 XJS, 4.0 litre, AJ16 engine.

I am in the same situation, needing the TPS reset. For me, my car was stalling and rough idle. A new TPS fixed it! But I have the resulting high idle 1300 - 1500 rpm.

I also did not get a response from the JLR web site.

So, I would like to get some more details on the genrad 3500? Since it worked I would like to buy from the same seller, if you recommend them. What is the added help you got from other members to successfully reprogram? Does it require a laptop?

Ebay is also advertising another programmer called TOAD, wondering if that would work?

Thank you very much, Patrick

 

I doubt that TOAD software works.

You need to take it to a dealer, or someone with a PDU.

Your only other alternative is the IDS. That can reset your TPS, but you may need to reset the Long Term Adaptations, which the IDS cannot do.

You could try it, by spending $150+ and possibly solve your problem, or you can spend about the same and take it to the dealer and definitely resolve your problem.

There's gotta be someone that can do this for you on the west coast.