My Jag xjr knocks as soon as drive or reverse is engaged, however back into neutral or park there is no noise at all. The car shifts through the gears great and the engine is superb. Any thoughts?

 

Welcome to the forum!

By 'knocking' do you mean standard engine predetonation? Real predetonation should set the CEL and a code. Got codes? What is your engine RPM in drive? Should be a little over 500.

Also, and just a WAG, any noise from belt drive area at low RPM? Belt tensioners issues have been reported from around your model year.

A dirty throttle body can cause idle issues. See GUS's description for cleaning here: Jaguar throttle body cleaning xk8

Let us know!

. . . and you would get a lot more input if posted over on the XJ (308) forum. Maybe one of the Mods will move this thread for you.

 

Supercharger drive coupler failed????
Torque converter faulty or fasteners loose.
Gearbox fault???
Engine bearings failing??
Piston 'SLAP'?????

bob gauff

 

Moving you over to the XJR section for 2001.

 

Thanks for your reply.
I don't belive this is a pre detonation noise and this is not an idle issue. The revs are indeed just above 500 rpm in drive. When you mention tensioners, the chain, fasterners, tensioners etc - these have all recently been replaced. The sound I'm hearing comes from the supercharger top cover area - and the supercharger is almost brand new, all supplied by local Jag dealer.

I'll get it in for diagnostics and see what comes out of that.

thank you again.

 

The only difference between reverse/drive and neutral/park is that in 1 case the engine is connected to the rest of the drivetrain and in the other one, is not.

Put the car in drive, step on the brake and rev the engine to 2500 rpm's
Is the knock still there?
If yes, the noise is load related and come from the drivetrain
If no, it is vibration related such as a loose heat shield or exhaust part banging around

 

The diagnosis finally showed that the issue is caused by the main bearings being on their way out. This car has had all the required dealer services throughout its life, every 3k new oil and filter, fluid changes, complete tune ups etc.
And to add to it, the transmission is now failing. Any sensible person could only conclude after $18k spent on repairs (over and above all the service costs) to this Jaguar within the last 2years plus the above horror story, that Jaguar Cars are an utter disgrace.

This is the very worst car I have ever seen.

Regards,

 

That's incredibly unfortunate. A car of that year is approaching the best of the model. I cannot understand how a Mercedes Benz gearbox, and main bearings can go out like that. I had a 2001 XJR cover 285,000 miles without failures, just servicing. It even had plastic timing parts. It's now powering an XKR without issue, (the engine and trans).

I guess yours was a late blooming lemon. Or it had a spell of sustained demands without fluids down the line.

 

That is unfortunate -- Your car should have the updated bearing?

How many miles?


Normally they are very reliable.

 

I bought my 02 XJL VP Jag at 56,000 miles, almost 5 years ago. Today it has 83,000 miles. The engine and drivetrain have been almost flawless with regular but routine maintenance, including changing some of the flexible hoses as preventive maintenance. A water pump was replaced under factory extended warranty.

My GUESS is that either: 1)You are getting some incredibaly bad (and expensive!) diagnositcs, or 2) Your engine/drivetrain has been subjected to some type of major trama that you don't know about.

That engine is usually very reliable and a good model year to buy now because many of the problems from the previous few years were solved.