How easy to rebuild throttle body?

[Davidqhog]

Morning All,

My Daimler SV8 took me 12 miles from home and then showed DSC failure, ASC failure and Engine Failsafe Mode.

I turned it off, waited 30 secs and tried again. Hi revs on start, settling to 1,000, same messages. Put it into gear and off we set at 10 mph. At least I got it home.

Local garage found the sensor connectors on the throttle body had worked loose and distorted a bit. They put them back and tried to correct the distortion and at least now it runs normally. But they think it will likely happen again and need a new throttle body.

These, if you can get them, run in at over £1,000. So, is it possible for a moderately competent person (me) to remove the throttle body, refurbish it and replace whatever sensors are dodgy. I've seen a couple of pretty bad videos on YouTube of work being done on them but they don't inspire me.

Any thoughts welcome.

TIA,

David Q

[Davidqhog]

Just to add to this,the codes I got were

P1121 - throttle position sensor inconsistent with MAF sensor
P1122 - pedal demand sensor A circuit low input

David Q

[BrianG]

David,
I suspect from your description of symptoms that the problem of the "sensors" relates to the throttle position potentiometers becoming worn. Remembering a Rover V8 EFi that I owned which had a worn position potentiometer, the hunting and high idle symptoms are similar, but with the then unsophisticated systems it did not prevent driving. The Lucas unobtainable throttle bodies could be fixed by replacing the single pot' as an external modification as I did, with one from many of the electronics stockists. As an alternative the Lucas pot' could be persuaded to work for a while by rubbing over the worn track with a soft lead pencil!

I'm not sure how many pots there are in the X308 throttle body but it will have at least two, like the X350, to ensure "plausible feedback" throttle position information to the EM computer - unlike the early Lucas EFi system. Your code P1122 indicates that one of them at least may have an open circuit connection to the moving wiper contact.

Stating the obvious, a quick fix option may be worth trying to obtain a working one from the breakers. Failing that perhaps obtain a scrap one which can be dismantled for investigation. I have not had the opportunity to dismantle a throttle body from either model of XJ but it might be possible to engineer a replacement solution once the internals are visible.

[Davidqhog]

Hi Brian,

Thanks for this reply.

I am thinking of trying Autoreserve Jaguar for a replacement and then looking at the current one to see if i can do anything to prolong its life.

From what I can see there are no new throttle bodies available for this car. SNG Barrett carry pictures but all stated to be unavailable. Sounds to me like we should be pressing for them to look into re-engineering them as I can't be the only person with this problem!

Regards,

David Q

[JimMann]

Hi David, if you need SNG Barrett to consider adding parts to the remanufacture list, you should complete a return via the "Spares Initiative" tab on this website - administered by Mike Horlor.

Click on the "Menu" tab above and in the drop down you will see "Spares Initiative". Follow the steps on there and send in a submission for the parts that you want to bring to the attention. If you need part numbers, you can search via the JLR Classic site, the address for which is:

"Jaguar Classic Parts
If you are looking for parts for your Jaguar, you may be able to purchase them from Jaguar Classic Parts. Have a look at https://parts.jaguarlandroverclassic.co ... 816351267/ for more information." Or you should at least be in a position to identify the Part Numbers. This note appeared in the most recent Regional Bulletin circulated to all Region Committee Members.

Jim Mann

[Davidqhog]

Hi Jim,

Good idea. I'm aware of the spares initiative.

I wonder whether it would be sufficiently lucrative for them though. I guess the X308 XJR & Daimler SV8 may share the same throttle body but I've fallen foul of that apparent similarity before! If they do, it may be worth their while.

I'll try it and see. Mind you, the ones they're showing as unavailable retail at over £1,000!

Thanks for the idea.

Regards,

David Q

[Davidqhog]

Well, sent the throttle body off to VCUS Ltd in Nottingham for analysis/repair. Sent it back as beyond repair but no analysis report. Asked for the report but no reply.

So, I now have a dead car!

I've notified Spares Initiative and left a marker on Autoreserve Jaguar for a throttle body.

TPS sensors can be had but is that the answer? Anyone have any ideas? Swallows Racing?

Regards,

Disconsolate David Q

[Davidqhog]

Inevitably, after a lot of searching and at one point coming to the conclusion that my lovely Daimler Super V8 was going to have to be scrapped, I contacted a few of the sages, Ken Jenkins, David Marks, Swallows.

Ken said it was too new for him (!), Swallows said that I'd tried everyone they would have - but David Marks came up trumps (sorry for that word).

He has these throttle bodies and can supply one, new TPS, scan everything and set it all up correctly. Only problem is he, not unnaturally, needs the car. So, hopefully this week, my local garage (brilliant Craig Bailey at Lechlade Motors) will transport it to David for repair and I'll get a train to Nottingham soon after to pick it up.

Expensive but worth it.