So i bought a xj6 yesterday and took it for a test drive round the block. It starts fine and drives fine up until about 100kmh but if you want to go any faster to say overtake or something it refuses to do so. So you feel it change gears but it doesn't rev out. I haven't picked the car up yet so I would like to get some ideas on what this may be before I drive 2 hours back to my town. Any ideas?

 

well XJ6s were not a great performance car anyway.

 

Well yea they definitely where not but they also definitely can go a lot faster. Not being able to get power when i need it is quite unsafe and needs to be fixed

 

Congratulations on a really unhelpful and total nonsense comment.

 

It may be tricky to diagnose if you can't run diagnostics on it before buying. There are some very knowledgeable people in here who will be along shortly to contribute some helpful theories.

 

Hi Killz,

Congratulations on your purchase.

These are great cars.

Performance wise whilst not straight line dragsters, nor supersonic missiles, these cars are more than adequate in everyday driving conditions.

A well sorted xj6 engine is surprisingly torquey and potent.

Lack of grunt over 100kph is just plain wrong.

Check for fuel starvation at high revs / speed - fuel regulator, fuel lines, clogged fuel filters restricting flow.

Check for timing problems - dizzy not set correctly, probably not camshaft related as you would have trouble with it running full stop.

Check HT leads - old worn out (internally) may not be getting a decent spark through which at lower revs seems OK but under load (higher revs) starts to break down.

Does the engine still run OK at higher revs, or does it start to run roughly before running out of steam?

Just my thoughts.

Good luck,

Nigel

 

My first thoughts are clogged fuel filter or clogged cat converter, if equipped

Cheers
DD

 

My car behaved exactly the same way when I got it, same speed even, and as Nigel and Doug have suggested it was a badly clogged filter. Hopefully it is that simple for you.

 

Indeed, a clogged filter will clip any car's wings - even a V8!

 

Thanks guys! Ill check the fuel filter, something with the fuel delivery was my first thoughts anyway. much appreciated

 

Welcome to the forum Killian, I see from your intro you have an XJ40. If you repost your question in the XJ40 forum you will get answers from members with the same model. Link below.

https://www.jaguarforums.com/forum/xj40-xj81-25/

 

Thank you, I do have an xj40 and ill ask future questions in the xj40 furum but this question is about my xj6

 

Didn't realise you had two jags. Now that you have added your cars to your signature it makes sense.

 

Has anyone considered that Killian got a better deal because of the "power limitation" ? I suspect it at least had to do with the PO's decision to sell.
Opportunity comes in strange ways...


As I dimly recall, the DOHC has two plugs near the outlet of the exhaust manifold. Whether they can be removed, sans a major battle or no in unknown to me.


But opening here would relieve any major back pressure caused downstream in the exhaust. Clogged cat/s included. Noisy, but if it runs better, there it is!!!!


Carl