2010 XKR

Driving back from London today I had to stop for fuel on the M3. Within 20 miles or so I started to notice a slight hesitation and misfire under light throttle (1500-2000RPM), plus a noticeable reduction in power and change in engine note. There was also a very abrupt deceleration and driveline snap when releasing the throttle.

Generic OBD reader showed P0101.

Turning to the great interwebz, I found this thread: https://www.jaguarforums.com/forum/x...08-xkr-137049/ and immediately realised that the problem had only started after refuelling......

Yup. I hadn't tightened the filler cap properly. 12 months of ownership, and it's always the silly things that catch you out

So thank you Ngarara (thanks tagged on the thread too). I hope you don't mind me starting a new thread, but as this is the only reference to this code for a post 2009 car, thought it might make things easier for other members searching for this issue on later 5.0 cars.

 

From my experience, one of your catalytic converters may have gone, same thing happened to me , exhaust note changed and powered down, left side cat, if you keep driving it if this is what has happened it may go into limp home mode as the car is choking itself and you'll be crawling home.
Hope it's not but if so mine cast around £1000 to fix.

 

Since tightening the cap properly the misfire hasn't shown itself and the power is back. Taking it for a 100mile round trip this afternoon, so fingers crossed.

Must read the Jag extended warranty paperwork to see if Cats are covered!

 

glad to hear your back in action, but don't mean to burst you bubble, but mine came back to life from time to time, but it was the cat, done the fuel cap thing also. Get it checked out, if you can get some one to give it some quick bursts of throttle and you listen underneath the car when it idles after a bit of throttle, around where the cats are, see can you hear a kind of rattle/jingle/buzzing noise from one of the cats, then the cat is gone.

 

Will get it checked out, but for now......

VERY spirited cross country blast - 100 mile round trip - this afternoon. No loss of power, no hesitation or unusual noise. One of the guys I was meeting up with is a senior member of the engineering team at JLR and I recounted the issue. He thinks I may well have got it in time.

I've checked the warranty paperwork and if it is cats, they're covered..

 

My pleasure - glad you got it sorted. I'm surprised that just leaving the cap slightly loose had such a significant effect. Something to file away for future reference!

Gawd, these cars are complex beasties....

 

In common with many petrol cars, the X150 needs a controlled vacuum on the fuel system. It's part of the emission controls (vapour release). If the car can't get a vacuum on the tank it leads to a series of errors building up, usually starting with P0101 (as this is the generic vacuum fault code across multiple systems) before cascading through a series of other DTCs (P0440, P0442, P0455).

Because all vacuum on the engine comes from one source, a loss of vacuum on the tank will lead to low vacuum on upstream systems, hence the MAF out of range (P0101) usually coming up first.

I managed to pull some of this out of my friend before he'd had too many beers..... the rest just comes from many years of amateur spanner work and a growing understanding of cascade failure reporting masking root cause (a lot of my work is in Quality Assurance and root cause analysis).

I'll still get the car into the workshop later in the week to get the non-generic codes read as my cheap ebay OBD reader only picks up the generic first level codes as the car would have been running rich for a few miles and may have fouled sensors or damaged the cats, as mentioned above.

Cheers for all your input folks, very much appreciated.

 

Thanks for this thread and the advice here and in the linked thread. I got the P0101 MAF error the other night. Had thrown the car into sport mode on an empty highway and CEL popped on. So of course came directly on here to search the problem. I went to check my gas cap and it pulled right out. I have actually gotten a "loose gas cap" warning before. I wonder if it is not tightened exactly 3 clicks if it comes loose? That would be odd. Regardless, the light went away. Hopefully that is the end of it, but will make sure I mention it to my mechanic when I bring the car in next time.