my 1998 Jaguar xj8 engine has developed an issue. The idle is rough, and the whole car shakes at idle (its feels sort of like a chugging,) it also vibrates between 45-55 mph. The engine has a bit of knock sound that seems to be coming from the front of the engine around the serpentine belt. I cannot pinpoint exactly where the sound is coming from, but it seems a bit louder on the passenger side. You can't really hear it with the lid closed, but when its open you can hear the knock. Has anyone else had these issues? I have been doing some research, and have decided it is either the engine mount, the timing belt tensioner, or the catalytic converter, or the transmission mount. The shaking at idle is worse some days than others. Can someone tell me where to look for the engine mount?? i cannot find a diagram anywhere, and my gut instinct says it is this. Again its a chugging and shake at idle and a slight vibration at 45-50mph, it has also stalled on mw right after cranking a few times. I had a new transmission put on like 2 years ago, and the car shifts just fine, so I am hoping its not another transmission issue. No lights have came on the dash.

 

The 2000 and earlier 4.0 V8s had problems with cam chain tensioners so I would take it to a dealer or a good Jaguar repair shop to get it checked out. If the cam chain lets go, you're probably looking at a new engine. Another weak spot for these engines is the water pump.

Mike

 

First off, there is no timing belt. These engines have timing chains. Second, QUIT driving it. Third, you probably have a bum timing chain tensioner/s. Maybe coils, but doubtful. The coils don't give too many problems.

IF YOU KEEP DRIVING IT, AND ANY TIMING CHAIN BREAKS, YOU COULD POSSIBLY BEND VALVES. THAT IS EXPENSIVE TO REPAIR. DON'T DRIVE IT!!! TOW IT TO THE NEAREST COMPETENT SHOP/DEALER.

On that note, if you do have tensioner issues, replace ALL of the tensioners with the updated units, replace the chains (4), and replace the chain guides. the guides are plastic and they all crack, and can break off. Also have the lower oil pan removed and all of the tensioner schrapnel removed. Oh, and it won't be cheap. Sorry.


Edit: Although the engine mounts are liquid filled and do leak after hard miles, these don't cause stalling, but can cause a BIT of a rough idle. Not like you are describing. The rear trans mount can be ruled out, too. Also forget the catalyst. You'd have a check engine light if one of those were defective. And if you keep driving it, the warnings will pop up.....it's just a matter of time.

 

Replacing the cam chain tensioners and associated parts will probably run you around $2000 or so parts and labor. Water pumps probably $500 or more. A Jag Tech would be a better source of pricing info. When Jaguar World ran an article about purchasing used saloons (sedans) they recommended budgeting the replacement of the cam chain tensioners and the water pump with the later 4.2 parts into your purchase price.

Mike

 

you guys were all wrong. I took it to the shop today. The rattling sound was the parts of the catalytic converter had broken off and were rattling around in it, it did sound just like a chain, but it was the metal filter looking part in the converter, had came unwelded. Also this was causing the chugging and the stalling. Thanks for the tips though! I am glad you took the time to help me with my issue.