I have a 1998 xjr with 74000 miles. it idles rough, has no power on acceleration. CE light is on, when i checked it with autozone it said cylinder #2 misfire.

i pulled the plug and it looked clean. after i put it back together i had the car running and unplugged the coil. i could definitely notice a difference. i switched coils with another cylinder and nothing changed. there is also alot of air coming from the valve covers and dipstick tube, and the intake is full of oil.

 

You need to do a compression test. One word, Nikasil...

If it checks out ok on the test, you need to sort the air leaks

 

thanks for the quick response. would the car be blowing smoke from the tailpipes if the nikasil lining was bad? my exhaust is really clean, you wouldnt know it had a problem while looking at it from behind.

 

Air coming from the valve covers and dipstick tube usually means rings, the Nikasil linings are shot, or something really bad like a hole in a piston. Pull the oil filler cap and see how much air is coming out of that. Your exhaust could still be clean with any of these conditions.
Vector

 

when i pull the oil filler cap theres alot of air coming from it.

 

Aw, I don;t know of anything minor that could do that. I would probably pull the head before I bought an engine, though.

 

well, when it first started running bad...i took it to a jag dealership, they told me it was the head gasket so i had them replace it. it still had the same problem. i think they would have told me if a piston had a hole in it, so im guessing with your help so far its probably nikasil. quick question, would a 4.0 out of a vaden plas be usable with my supercharger in this car?

 

To make a good supercharged engine out of a 4.0VDP unit is a fair bit of work, but it can be done if you're into building engines. For me an interesting project, but if your going to rebuild the engine, it'd be better to use a S/C short motor, i.e. the block, crank and pistons.

The main reasons for this are as follows....

The S/C unit has a lower compression ratio, meaning the pistons are different to the VDP normally aspirated engine.
The cylinder heads are different between the two, meaning you'll have to keep the heads from the S/C engine, the VDP engine has variable valve timing, with the inlet cams being different. The cam covers are also different. The engine control module in the S/C car will not be able to actuate the VVT.

Alternatives, to have the block machined and steel liners pressed in. Or, to have the block re-nikasil coated in the bores. Both expensive, and you'll need to find a specialist who can carry out the work.

My suggestion is to find a steel liner engine, a short motor. Use all ancillaries from your engine. You could even use the 4.2 unit (steel) with some work, and using your heads.

But, having seen a rather naive question, i.e. just bolt the supercharger to a N.A. engine, I suspect you'll not be knowledgeable enough to do any of this work yourself. This means paying someone. This means a rather large bill. I don't want to get you downhearted, but many car's here in the UK are scrap now because of this issue. At best, parts cars. It's not just the XJR, XKR's, which are more valuable have the same issue, good steel liner engines are at a premium, you'll find these engines fetch good money.

 

thanks for the response. I have been around the block a few times being a mechanic, although i am new to Jaguar. I just wasnt sure if they were formatted similarly.