Recently purchased a stunning 1998 xjr on very low mileage and been kept inside all it's life. All the welding had been done, seems too good to be true. Then after finding some tell tale signs of wear and finding oil in place, I dug deeper and performed a pressure test. 4 out of 4 cylinder were in the range of 100-130 and the other 4 above. Issue im facing is do I bought another 2nd hand engine in it or do I swap it with a different V8 engine e.g. LS

 

Have you been driving the car at all?

 

yeah, since owning it i have put around 100 miles on it. Noticed a rough idle but this is my first V8 so was unsure if they are just naturally lumpy.

 

No, idle is not normally lumpy. (No Chevy lump either.) Which four cylinders? I hope compression is not low all on one bank. If so, I'd suspect timing chain tensioner failure. Nothing to do with mileage, rather age. 1999 these things had timing chain tensioners made of plastic which at this point is brittle and prone to crack. It can lose hydraulic pressure and jump time. Its pretty common to fail only on one one bank of cylinders. I think I recall reading some posters say they'd jumped just one tooth on one bank and it still ran, but poorly. But any little hiccup can set off those brittle plastic tensioners like nitro glycerin in an old western movie, grenade the whole valve train and send shrapnel into the oil pan. And even tho its got timing chains, its an interference engine just like many 4-cylinders with rubber timing belts so don't even start the motor again until you confirm whether or not the tensioners have been upgraded If you haven't already, you need to review the maintenance records to look for a receipt for tensioner upgrade or pull a valve cover and physically lay eyes on them to confirm if they are plastic or metal bodies. Post back what you discover and we'll point you where to go from there. Hopefully, I'm just assuming the worst, the tensioners have been upgraded and its really something cheaper to fix (cause I'd hate to see another Jag get lumped )

 

Look for the engine seriel number to determain if a early AJ26 or later AJ27 engine

There is famous AJ26 engines with compression issues ( ate up Nicasil ( sp ) not steel sleave cylender walls , AJ27 has steel )

You can also place the engine in a bore wash condition based on short runs like driveway that you can easily get out of

This has nothing to do with timing but others would know if your seriel gets you into improved timing chain mechinisem or not or a quick identifier maybe as I think I saw someone post such

Now I read the previus post

 

cylinder

Here are my compression results, the low compression is spread out over the both banks. Timing chain sounds fine with no sounds of rattle on start up or driving but i do beileve its on its orginal tensioners

 

Back then, there was a recall for the Nicasil coated cylinder-bores. But that does not guarantee that all previous owners made use of that offer having part of the engine swapped back then.
Hence, IF it is one of the Nicasil engines, there should be a plate installed in the driver's doorframe confirming that the recall-modification had been conducted. If not. then it needs to be tested, what the status of the engine is. If it is still good, there might not be too much to worry about, because if it is a non-swapped Nicasil engine, if might actually do well these days as the petrol use today is different to the petrol of back then (I think the issue was that the lead in the petrol back then destroyed the Nicasil coating)

And of course the timing chain-tensioners and guides (if those are still the original ones, which were inept for their purpose) need to be swapped, in case that has not been done yet - and on a low mileage car previous owners would not have seen the need to swap them:

I wrote a DIY guide about that, but note, that my X308 is not supercharged and does not have VVT:
https://www.jaguarforums.com/forum/x...e-swap-266724/

Also: Use an OBDII scanner to read out the failure codes.

...if there are problems with the current engine, it is not wise to contemplate as very first solution to put another old engine in, which might be worse than the one, which is in there - apart from the troubles of swapping them...

 

Jaguar used Nikasil blocks until August 18 2000 when they were experimenting with CAST IN and SHRINK FIT liners.

I made .jpg copies of a memo I got at Jaguar training when they were trying to explain the problems with the AJV8 blocks.

 

Someone correct me if I�m wrong but, wasn�t Nikasil engine failures hit the hardest over in Europe due to the higher sulfur in fuel vs the USA?

 

Low mileage i would engine soak
It's unlikely to need another engine with low mileage xjr

 

Yes, Addicted, it was sulfur.not lead. I knew it was something, which was in high concentration in the petrol back then, but is not as high these days.

I just asked my browser AI, and it says:
This issue was primarily caused by high sulfur content in fuel, which varied widely across different regions. The Nikasil coating would break down over time when exposed to high sulfur fuel, allowing the piston rings to score the cylinder walls and reduce compression.

 

That Petrol came from Venezuela - you would see virtually new Jaguars and BMW's long cranking in car parks - it was cheaper, supermarket forecourt fuel. Nowhere near the likes of Shell V-power.