So I pulled into a friend's shop and we were looking over some vintage Corvettes and other American iron and when I went to leave my XK8 with 63,000 miles (20,000 of them mine) idled like a paint shaker. Ran fine on the way in, barely ran on the way out.

I pulled the codes and found a generalized misfire across the #1 bank. The JTIS pointed toward a variety of causes from coils to valves. I checked what I could hoping for a simple electrical cause (bad connector, etc.) but found none.

Many dollars later the technician found the timing chain tensioners were worn through and the chain stretched enough to let it skip a tooth. Many, many more dollars later I have a complete new set up including new fluids all around.

I don't have a particular reason to doubt the technician - it is a wear item and there are lots of forum comments about the cam chain tensioners on this engine but it seems to me that 63,000 miles is a bit slight for this level of work. Oddly, I had been listening for evidence of the upper tensioners going bad - if it did make noise I evidently didn't know what I was hearing!

My earlier Northstar 32 valve DOHC V-8 was indestructable through 80K miles, and are routinely good through 150K miles.

What gives with Jaguar engineering or choice of materials?

 

Hi Scott
I had something similar on my 97. The one tensioner was messed up and needed to be replaces around 50K miles. Runs great now. Fortunately, I purchased an after market warranty when I bought the Jag at 24K miles. So, the price tag wasn't too bad for me. I recall seeing the old unit (or what was left of it) and seriously wondered why that particular material was chosen for that part.
Good luch
Ed K

 

On my 97 a tensioner when at 70k. i knew what the warning signal was since I had researched the car here before I bought it. Sure enough just like you, it ran fine when I parked it, came back out of store and heard the rattle and bad running. Shut it off, that was that. It it was a tensioner on the pass side of motor. Chain jumper a tooth also.
Know issue through like 2000 I think.

 

I looked (again) through the forum and am somewhat pleased that I probably didn't bend a bunch of valves. Let's hope what little luck I have holds out when they fire it up this afternoon!

I'm sort of stuck out of town with the thing and wasn't able to search out a specialist, so I'm stuck doing the repairs at a dealership.

I'll update this afternoon...

 

I had the same tapping noise. I originally took it to the garage thinking that it may be a valve tap. Scary thing was that much of the tensioner part was gone. Apparently ground up and flushed out over numerous oil changes.
Later
Ed K

 

It's done, no valve damage.

I may move on to another car. Maybe back to Cadillac with a CTS of some flavor.

Overall, my experience with the level of Jaguar I can afford is 50/50 I guess. Over the 2 years it's kept me on my game in terms of diagnostics and home repair; it's a beautiful car and the forum community is nice without a doubt.

We'll see how the next couple of months go. It would be a great second/summer car but I need it to do more than that. There's an all-British show coming up in Chicago in a few weeks, I might put a sign on it there.

 

Now that she's (your car) has heard that, she won't be giving you any issues for months. Mark my words, the kitty just knows when she's bad and starts to behave.