www.jec.org.uk

Hi Everyone,
I have owned a 2004 Jaguar XKR in slate grey with ivory interior for the past two years and it has now covered some 42000 miles. It has a full and comprehensive service history which I have maintained and I have never had any concerns with the car. I am currently in Scotland with the vehicle on a touring holiday having arrived on Friday. Everything was going fine until today. On setting off from Fort William this morning I thought the vehicle was " hunting ", revs going slightly up and down, when cold at 30 mph. I filled up at Morrisons, I know stay away from supermarket petrol but I was desperate, but when warm the car was running fine, or so I thought. We had been going for approximately 45 mins at an average speed of around 55mph. Whilst going up an incline I noticed an orange warning notice appear in the information centre, "RESTRICTED PERFORMANCE". I pulled over and switched the engine off and read my owners manual which basically says visit a dealer. On switching the engine back on after about 5 minutes the message had gone. I drove the vehicle in normal auto with no apparent loss of power and put it into third and took it to 4500rpm again with no adverse effects. I then drove, by the shortest route, to our overnight stop in Dornoch near Inverness. This was probably a further 75 miles of open A roads averaging 60mph. The warning has still not re appeared. Is this something I should be concerned about or should I carry on and have it seen when I get home next Saturday. I am considering cancelling my trip and taking it easy going home tomorrow. Any advice or reassurance would be greatfully appreciated.
Reg Page

If it's running ok I would wait and see, I have lost count of the number of messages that come and then go, on all the jags i have had. Perhaps the latest models are more reliable, I wouldn't know! So many different things can cause the restricted performance message, in theory the car goes into 'limp home' mode designed not to stress the transmission and engine, but you would definitely notice a sharp drop in performance if that happened.

Very generally, the higher the compression ratio of a petrol engine the more the RON value away from manufacturer's requirment can affect performance. But never heard of 92RON (a Sainsbury garage checkout lady actually 'phoned head office for me when pump sticker just said: "This fuel conforms to BS<bla><bla> etc...) causing a MIL

I experienced (with my 2L tuned-tFSI Passat to 245BHP now sold) noticeable performance differences between 95, supermarket "95RON", and Tesco Momentum 100RON or Shell VPower 99RON. Only Tesco for supermarket prices keep RON stickers permanently on pumps -- Sainsburys, Aldi, Morrisons did, but over the past years now don't

I think there's a difference between 95 and 99RON with my XJ8 -- but this could be just self-perception -- like a car seems to go better after a wash 'n shine...

Thank you all for taking the trouble and time to reply. I did not feel confident with the car after this episode and so took it to the main dealership in Inverness to see if they could help. I had to leave it with them for the day on the off chance they could fit it in. I called back at the end of the day and they had done a diagnostic session on the car. They said it had several, what they referred to as old codes stored, but they said nothing that was recent?? The technician said one of these related to the throttle. The technician cleared the codes and test drove the vehicle and said it was OK. He stated they could obviously not fix a fault they could not find. They said I should use the vehicle to see if the fault re occurred. Not really a satisfactory result but on the face of it,little else I can do if nothing is now showing as a fault. I'll keep my eye on it and report back should anything else happen.

Thanks again all,

Reg Page

Hi Reg,

There will always be a lot of old codes, I used my code reader the other day trying to fix the damn parking sensors again (GRRRR....!), and was fascinated by all the old fault codes stored. Don't forget this is just the car's computer interrogating all the systems on start up, and it will log anything that is not quite within the right parameters. It doesn't necessarily mean anything is wrong. If the car is driving fine and it doesn't happen again then ignore it. If it repeatedly comes up then it probably does need investigating with a decent code reader. If possible steer clear of main dealers as they can charge up to £100 just for a diagnostic check. Another common cause of repeated spurious codes is an ageing battery.

If you have the work done that's indicated as necessary by a diagnostic check that you've had done and paid for previously, the main dealer will often credit you that charge in their final bill. But you have to ask for it

That seems to have become the norm at VW dealerships anyway -- think I heard JLR's have the same policy
Mind you, at £134 / hour +VAT but the number of hours' applied according to the dealer's charge-out manual, I'd hope so too

A dealer diagnostic doesn't take an hour shurely?

It may not take an hour but that's what they charge for!
£134 + VAT (ie a total of over £160) certainly makes investing in something like the iCarsoft 930 at £90-95 look like a bargain!
Equally there are many independent specialists equipped with the Autologic system. These are every bit as capable as the main dealer systems. I've even heard stories of main dealers spending days with cars hooked up to their software with internet connections to the factory and still not being able to solve the issues and an Autologic sorting it in 10 minutes. Many independent specialists will also not charge for diagnostics if they get the repair job - and their labour rate will be half that of the main dealer!

I agree, well worth the investment. Most dealers have a minimum charge of an hour, though the job probably takes about 10 minutes...