Trying to solve a rough running x308.
Reading are
1 - 95
2 - 100
3 - 145
4 - 145
5 - 120
6 - 95
7 -95
8 - 0

I recently replaced the valve cover gaskets and spark plugs. When i was removing the new spark plugs, I also noticed that spark plug 8 was completely clean as if theres no combustion happening at all in that chamber. Swapped coils from 7 to 8 and still looks the same. Also did a combustion gas leak test and it did not show any change in color.

I went from having 12 codes and misfires on all cylinders, to only having a p0057 Heated control circuit low bank 2 sensor 2. (o2 sensor) I have not swapped this out yet.

 

I think I would try a little oil in number eight cylinder and see if you can get some kind of compressions started if that doesn’t help I would start thinking that Number eight valves are staying open at some point and not letting compression build

 

Zero compression is usually a serious matter. However it could be a bent
valve or a seating problem. If it is not backfiring, then it is probably piston
or rings related.

 

Check the fuse for the heated O2 sensor first before replacing. Should be fuse 11 (30amp) or 14 (10amp)

 

I don't think fuses could cause zero compression.

 

I once has a small bolt that got stuck in a valve so it did not close. You could hear the back pressure in the manifold.
I'd also try putting some regular engine oil in the cylinder to see if that helps or perhaps if its a stuck valve something like marvel oil through the throttle body? If you can get it fixed without pulling the head that would be best.

Reading are
1 - 95
2 - 100
3 - 145
4 - 145
5 - 120
6 - 95
7 -95
8 - 0

I recently replaced the valve cover gaskets and spark plugs. When i was removing the new spark plugs, I also noticed that spark plug 8 was completely clean as if theres no combustion happening at all in that chamber. Swapped coils from 7 to 8 and still looks the same. Also did a combustion gas leak test and it did not show any change in color.

I went from having 12 codes and misfires on all cylinders, to only having a p0057 Heated control circuit low bank 2 sensor 2. (o2 sensor) I have not swapped this out yet.[/QUOTE]

 

I was responding to this... Kind of thought it was obvious?

He has one of 4 issues for 0 compression, as already stated,..bent valves and/or broken rings (somewhat inclusive, perhaps hole in the piston?). The others being a blown out the back head gasket (would make noise though) and/or a cracked sleeve. I'd be checking the oil for fuel residue and not trying to run it because of that. If so or you'll torch your bearings and that's a whole new ball game.
With the lack of burn on the plug, it seems quite obvious the fuel is exhausting before detonation, thus the issue really points at stuck open/bent valves or hole in the piston? Pull the cover and if possible, put a bore scope in the plug hole to check the liner and piston top.

 

Well. Enough with theoretical situations. There is a decent size hole on the side of the piston.
I guess now the question becomes part it out or replace the engine.

 

It depends on how bad the rest of the car is. That engine overheated badly. I believe the 99’ XJR is still an AJ26(?). You could get an AJ27 S/C engine and swap over the AJ26 components onto the 27 and make it work. DO NOT toss out the old engine before the used 27 engine is running. A few years ago another forum member did that and had to locate an AJ26 flex plate.

 

That sucks Linas...sorry about that.
Supposedly the AJ27 was introduced in MY 99...Addicted is correct on the swap if your going that route...CYA.
I don't see where he may have sold the motor yet, but he isn't too far away to say in VA... https://www.jaguarforums.com/forum/market/259372

 

be sure to throw the old engine in the trash. i have all types of aj26 accessories i need to sell 🧍‍♂️

 

 

I have a slightly used AJ26 throttle body if you want to add it to your list of stuff to sell.

 

Oh boy! I have had my share of engine swaps and not all with the
same degree of success. I have found it is difficult to gage the status
of an engine without is being on the road.