Hi,

I would love to hear any members thoughts & sugguestions regarding the situation below.


I recently was given a 1999 Jaguar XJ8 which I have taken on as a "project car".

Last fall the car suddenly turned on the check engine light and started running in restricted performance mode. The car has about 95,000 miles on it. Up til then the owner (a friend of mine) reported the car ran fine.

The condition of the car is such that the check engine light is on and a scan tool reveals P308 & P1316 fault codes in the computer. Although the car idles rough, I would not consider it hard to start (in 70+ degree weather). Also the car apparenly does not burn oil (no smoke, blue or otherwise come out of the tailpipe).

The car was given to me on the notion that the engine block is hosed due to the Nikasil coating used on the engine block. Before I go through the process of taking the engine out (or remove the head(s) ) I am going through some basic troubleshooting on my own.

The 1st thing I did is hooked up my scan tool and read the codes out (above). I then cleared the codes, let the car run for a few minutes and they returned (no surprise).

Next I looked at cylinder number 8 (Bank B 4). I took the spark plug out and it looked normal. There was some very light brown stuff on it but nothing out of the ordinary. Nothing I haven't seen before on other cars I have worked on. I also compaired it with some pictures of various spark plug fowling and it looked almost exactly like the "clean but used example".

I asked the previous owner how long the plugs were in the engine (not factory) and he said they were changed about 10,000 to 20,000 miles ago.

Next I swapped the ignition coil pack on the cylinder with another "good" cylinder. Reset the codes, ran the engine, codes came back. No luck there.

Next step I performed a leak down test on the cylinder number 8 with the engine cold (not run for a day). The leak down test showed 60% leak down thru the cylinder with most (all) the air coming out through the PCV port.

My heart sank at this point as I thought this confirmed my worst fears. I went through the exercise of performing the same leak down test on 3 other cylinders and to my surprise 2 showed 60% leak down (same as "bad" cylinder #8) and the other one showed about 50%. All were leaking thru the crankcase (PCV) port.

I also should note the spark plugs looked great on all of the cylinders.

I was somewhat encourged by the fact other cylinders are leaking down about the same. So I went to the next item - fuel. My plan was to swap the fuel injector on cylinder #8 with cylinder #6

In the process of removing the fuel injector on cylinder #8 it basically fell apart as I tried to remove it. The bottom piece of the fuel remained behind as I pulled it out. In fact the remaining piece was lodged in there *really* good. I had to run a big screw down through and pull it out with a lot force - but it all came out.

So now I am waiting on a new fuel injector to try my original troubleshooting plan. But I curious to know what you guys think about the situation.

I would be sold on the cylinder bores being hosed (scored) except for 3 things.

1) No evidence of oil burning. Spark plug clean, no tailpipe smoke during running and reving up.

2) the fuel injector came apart when I tried to remove it.

3) the car seemed to run fine up to 95,000 in 2008.


Is there a possibity that only the piston rings are worn out?
Is 60% leak down on a cold engine that outside of normal? (I would presume so).

Is this Nikasil?


Thanks so much....

 

Did you try a "wet" compression test ? These engines have low tension rings, and if the cylinders get washed with fuel, they will lose compression to the point of non-starting. This is not uncommon. Try running the engine until warm and give it a shot, but I wouldn't conclude the cylinder bores were trashed just yet. Check out the secondary cam chain tensioners also. The car should not idle rough. There is a lot of info about this on this web site and a bunch of others. The cam chain tensioner problem is a lot more common, and you want to catch it before it starts destroying things.

 

I did a "wet" leak down test. I squirted a little oil in the cylinder and the leak down dropped to like 5% in 2 different cylinders.

Strangely enough I have not performed a compression test yet - just leak down.

I cannot seem to find a consistant set of clues that points to the cylinder bores being trashed. Ultimately there is only one way to know - and that is to remove the head.

Yeah, changing out the chain tensioners is definately on my list. I just need to find out how bad off the car is right now.


Thanks...

 

Interestingly enough replacing the fuel inject may have did something. I no longer have any fault codes and all of the lights are off (for now).

The compression test on cylinder #8 is still really bad. About 50 PSI, the cylinder next to it (#6) is about 75 PSI. I removed the PCV hose while the engine is running and there is so much blow by coming out that you could dry your hair with it.

So next thing I am going to try for a quick "limp along" fix is the engine restore oil additive. Does anyone know if this stuff will harm nikasil coatings?

I also have another question for the Jag experts. I read a comment that the engine had to be removed for the piston rings to be replaced, is this true? If so, why?

If I take the heads off and the bores look OK, I will probably try to replace the piston rings to attempt to get compression back to somewhat normal. But if I have to remove the engine to do this I will probably do that and have it bored out and sleeved with iron liners (then to a full rebuild). I dread the idea of removing the engine from the car.....


Thanks for any help/advice!