2001 XK8 and it is back in restricted performance mode- Now, what could it be?

Well, after a successful repair a couple months ago, we are back to ‘restricted performance’ mode. I have been driving it and it has been just great until tonight. Went a couple miles under 3000 rpm, and it was fine. I like to give it a little gas and on comes the message! Pulled back into the garage and first thing; check the oil, as the engine light was on. On minimum, but will add a quart after the holidays. Could that be all it is? No idea these things leaked oil like the old days, or burned it, but here we are…Garage floor looks dry.

My experience with Jag engines is they take a long time for the oil to drain down after running. I’ve made a practice of only checking the oil when the engine is cold, first thing in the morning. I check the fluids on a Saturday morning before heading out for the day. Avoids the chance of overfilling the engine.

What was the repair? Could be the same or similar problem. Do you have a scanner?

Eight plugs and two coil packs. I see where you are going. Car is a 2001 with 81000 miles. And yes, I have a scanner. Any codes to look for? I have ABS light on all the time, but don’t care about that one. Prob. one of the wheell sensors.

Good advice. I will check it tomorrow morning when it is stone cold. Oil check

Yeah your approaching the dreaded 100,000 mark
Did you do the tensioner sand chains?
Did you do the Pcv pipe cleaning
I love your car BUT
100,000 was the build criteria 101 and boom
Ps make sure your cats are good!

Funny you mentioned the cats, as that was all that the one garage could come up with as a possibility. Turns out, garage #2 found the problem with 8 new plugs and two coil packs. I thought by 2001 all the tensioner scares were over. No noise at all, car is like glass when running. PVC pipe cleaning? Very strange car. It is all about looks, and that engine should have been completely sorted out before they even sold them. My thoughts right now is to find a willing buyer, take what I can get for the car and run like hell. A real shame to dump something like this on the public, and they wonder why they have a lousy reputation. Of course, plan B would be a swap to an LS/GM tranny. Kits are out there and would cost about as much as the fixes on the Jag.

If the AJ-V8 cars were “100,000 mile” cars then E-types and all other 60’s Jags were “50,000 mile cars.”

If you don’t know what codes are being thrown then you don’t know what’s wrong with the engine. In my experience, “restricted performance” has almost always been a P0171 or P0174 code - i.e. engine bank too lean. This in turn, usually is a leak in the intake system.

Don’t think the dealers with factory service will surely figure it out - I paid to have a dealer try to track that code on my S-type R, and they insisted it was plugged or bad fuel injectors and wanted me to do a $1,000 cleaning. I did not accept this diagnosis, and after a few months of research and troubleshooting, found out it was an air bleed hose fitting running into the throttle body that had disintegrated.

On my X308 XJR, it was virtually invisible cracks in the plastic intake duct behind the air meter. And in one more case on the S-type R, it was user error - I forgot to tighten the clamp holding the hose to the air meter.

Of course, it could be something else too - but only the code will tell. As far as the 100,000 mile car business, if my X308 hadn’t been wrecked, it would have long passed the 100,000 mile mark and be entering its 21st year of service. My S-type R is approaching 100,000 miles and 16 years of operation. I have no concerns that it’s on the edge of self-destruction.


The x300 was Over Built to put Jaguar almost in competition with a new company called Lexus.
Almost keeping up with Mercedes and BMW as well, they did and the sales and loyalty proves it out.
As they moved onto the x308
Plastic thermostat housing
Fuel pumps
ABS system
Rear view mirror goop on dash
Terrible wood on dash turning to milk
Transmission that self implodes at 100,000
And cheap muffler materials rotting away
All helped in creating a 1,000 dollar car special
That people endure today
They look great and new were easier to drive than the xj6 but…….
It was a MASS production car built to a 100,000 mile limit
Yes old Etypes were 50,000 limited the way a series 3 xj6 fell apart at 30,000 miles
Only the x300 can stand the limits
It’s old now it’s quirky a bit but it’s the last diy and the door cards don’t fall off at 50,000 miles

Well my 100,000 mile XJR is going well and I’m see no reason why it should expire in the next few miles. The only real trouble I have had with it was the MERCEDES transmission when the input speed turbine failed, the other major was the diff which I managed to blow up due to over enthusiastic cornering. Oh and the major remodelling I did to the front sheet metal.

Robin I had an 2001 and 2003
I hope you get a million miles out of them
And you just might
Like the dreamers and bench racers in the Etype club
Reality becomes a memory from driving an Etype 45 years ago
They never leaked
They did 150 mph all day
Stopped on a dime and
Never had an issue with electronics
I never saw the Etype on top of lifetime jd powers ratings🤣
Now I’m having fun with you and owned your car new , drive it till it blows
That’s what I’m doing today!3

From my research when replacing coil packs, all should be replaced. When I bought my 01 XKR it was doing the same thing. I replaced all the plugs and all the coil packs and have had no issues since.


Well said, and my thoughts exactly. The ‘patch job’ with just two, on a twenty-year-old car, temporarily fixed the problem. Will read the codes and see what’s up first.

My beef is that the car was overbuilt, and has too many extra features that only complicates matters when it comes to servicing. That diagnostic run-thru is crazy, and it shows the lengths of absurdity. I turned the key and it lit up trunk open, door open, hood open (all in American}, along with an engine light, an abs light, and an ASC warning message Who or what in the hell was Ford trying to impress. They got the body right, but the rest is crap.

It’s not Ford, that’s all Jaguar. Fords of the same year don’t have these problems (shoddy plastics that decay and cause the tensioners to fail, intake leaks, and the thermostat to disintegrate, bad solder joints in the ABS module that throw the anti-lock error messages, and a fail-safe mode that kicks in when there’s a throttle body potentiometer discrepancy - reducing you to 15% power when you’re trying to merge on to a freeway.)

If there were more Ford influence, maybe those problems wouldn’t have happened. And today’s Jaguars, a decade plus removed from Ford, still have similar issues.


I had exactly the same problem: restricted performance. So, bought an OBD-reader (20€), got the error codes (6), deleted, test drive, they appeared again, deleted, test drive, appeared again… so, then started reading and tracing what’s wrong. Pointed towards cylinder #4, its spark plug, ignition coil, or air intake censor. Changed all 8 spark plugs (dealer did this previously 11y/34tkm ago), that ignition coil, cleaned throttle body, changed air filter. All this first time in my life. And it looks now working, knock-knock… So, check the codes and then you know what to do.

Those are awkward years for ALL
Manufactures and there lies the non collectible saga of most modern cars.