Hi Guys,

Just wondering if any of you have any ideas???

Over the weekend in the wet weather my XJ8 has been going in and out of Restricted Performance or limp mode. Where it will not rev over 3000rpm and judders if you go over 50MPH.....

The first time it did it it was just for a moment, the other times it did it they were for 5-10minute periods.

Any idea whats caused this? Fired it up today for a small drive and was fine.

All help will be appreciated

 

Louis - are you aware of the fact these car's log faults, to capture these faults you need to plug in an OBD reader to pull the codes.
Many things can put the car in restricted performance, at this point it's guess work. With the fault codes we can ID it and point you towards a fix. The ELM 327 OBD reader is a cheap and easy option to pull them and post on here...

 

Did you replace the wrong spark plugs?

 

Must be a virus or so

I am experiencing exactly the same problem: After the recent cold spell I took the Jag out for a drive. It started up with no fuss at all and ran smoothly halfways around the M25 when all of a sudden the 'Restricted Performance' light came on and the car started to judder big time. At the time I was driving smoothly with no sudden change to load or speed or anything.

Slowing down to about 50mph and changing gear to keep the revs around 2500 rpm made the 'Restricted Performance' light go out for a while but the car was still juddering a little. Same at 70 mph: as long as the revs are between 2500 and 3000 the car ran more or less smooth. Anything below and it would judder like hell.

Took the car in to two different garages (not specialist Jaguar garages I should mention). After lots of headscratching they both eventually suggested the timing chain had jumped a notch and was causing it. Repair costs approaching the value of the car Me not very happy.

I'm not a car mechanic, but since student times I have fixed a few things on my cars myself, so I am trying to get to the bottom of what it could be (never mind the repair cost).

I have heard about the XJ8 V8 4.0 engine being prone to timing jumps, but for three reasons I find it unlikely:
a) the tensioners had been replaced about a year ago after one of them started to make a noise like a siren.
b) what would cause the chain to jump when the engine was rev'ing a smooth 2000 rpm with no load change?
c) It happened after the car had reached proper operating temperature, again I would expect this to happen when the engine is cold.

The second mechanic at least replaced the spark plugs and by the looks of it they have never been changed (mechanic no. 1 lost me as a customer, since I had the car regularly serviced with him. Not impressed!)

While Mr. Better mechanic worked on the car I looked over his shoulder and made a few observations:
The left bank (no.2) was pretty oily, with Plug no.6 (second from the front) almost drowning in oil.
Right bank was completely dry.

The coils appeared to be all in working order, as you could hear the sharp crack when they fired (he pulled them out one by one to see if it made any difference (not that I could notice any on the left bank).

With the new spark plugs the car runs a lot smoother but still judders in low revs and when I'm driving it, the 'Restricted Performance' light comes on every so often.

I had a go at the OBD2 diagnostics and below are the results listed. It certainly doesn't look good for the left bank!
Besides of the codes I also noticed that there was no reading from the no.1 O2 sensor. The no.2 seems ok.

Here's the codes:

P0300 Random/Multiple cylinder misfire detected
P0305 Cylinder 5 misfire detected
P0306 Cylinder 6 misfire detected
P0307 Cylinder 7 misfire detected
P0308 Cylinder 8 misfire detected
P1314 Misfire/catalyst damage (bank2)
P1316 Misfire

These re-appeared after resetting the system.
Another code appeared the first time around but disappeared, said something about system too lean.

Any suggestions anyone?

The car is otherwise in very good condition, trim and paintwork and all, I would hate to see it go

 

Hate to say it, but misfires along one bank do suggest a timing issue between cam sensor and crank sensor there is a problem, the likely cause is a skipped chain.

I would suggest pulling the cam covers and checking the cam flats are correct - there is so much info regarding this that a quick search will yield many threads on similar issues.

The oil on #6 plug is likely a failing plug boss seal.

With #1 tech, did they carry out a full timing chain tensioners and guides job or just the secondaries?

 

Hi Sean,
thanks for your quick reply.

As far as I know, the tensioner replacement was a full job, it was done by a Dutch garage that specialises in Jaguar restoration. In fact it was the first thing he suggested when I turned up. I remember him showing me the main tensioner: a little piston in a plastic casing (which already had a crack).

At the time I had a more pressing body work issue due to an unplanned encounter with a Belgian lorry so I wasn't really that focused on the engine issue. He just told me that this was something that needed doing on all V8 engines.

He did a marvellous job in removing all traces of said lorry and the engine ran absolutely smooth and pretty efficient as well thereafter, getting 30+ mpg on the motorway.

But it isn't really very practical to have your car serviced in Holland when you're living in Herts, so I picked a local garage. Should have known better.

I'm considering limping over to Holland and have it sorted there. Probably cheaper as well.

Will check the cam alignment before though. Job for a weekend.

 

Not sure whom you might have used in the past. But I can recommend G&G in Heinkenzands.

https://gg-autoservice.nl

Good luck

Jeroen

 

I used Classic & Ko: dienstverlening op autogebied! in Vorden. Close to friends of mine, so quite convenient. Very professional team, both for bodywork and engine.

 

Hi,

I know its been a while since I started this thread, but the problem is becoming more regular!

I have got myself an OBI reader and I have plugged it in tonight and it has come up with P0355??

Any ideas what fault this is/how to fix this?

 

 

I had the same issue with my car and it was the battery was either dead or the conectors were off base

 

I had the same issue some time ago and the cause were the spark plugs.
Turns out the garage hadn't bothered changing them (you need to remove the coil pack on top of each spark plug first).
When I finally took them out myself, they looked absolutely decrepit.
I replaced all eight of them and the engine ran very noticeably smoother. Limp mode never came on after that.

This would be my first port of call.