How can I decarbon my cylinders on my 1995 XJ6?

Many thanks.

bliving7

 

In answer to your question:

Drive it,tank full of the best quality fuel you can find. Vary the driving style, but mainly "hard".

Are you sure it has carbon that needs removing. These modern engines do not carbon up like the old generation did.

You have other posts, so i will go read.

 

Many Thanks Grant.

Bought my first Jag, new, in 1982. My son and/or I drove it until last year when his garage got too full. Still driving them.

Anyway, my thread from yesterday was misleading. My '95 XJ6 with 220,000 miles ran perfectly until it sat for two weeks. It became a no starter after that.

That has happened once before and the car was towed in my my mechanic. Turned out to be stuck rings. That is what I think is happening now. I hooked a compression tester to it this afternoon and all cylinders were in the 20-40 range except for two and three. They were up in the nineties. But when I removed the plugs I found that the cam cover gasket had been leaking and there was oil about 3/4 inch up the coil boot. That oil then ran into the cylinder I'm guessing.

My mechanic last time put transmission oil in the cylinders and was able to free up the rings. That is my plan this time unless you have a better idea.

Many thanks for your help.

Bill Livingston
Hot Springs, Arkansas
USA

 

The oil may have caused the coils to short. There have been many reports of coil failure due to oil in the plug wells.

 

The mud clears somewhat.

The oil in the wells will be in the cylinders, gravity does that.

The trans oil fix is a good one, and works for me.

The so low in the 4 cylinders is odd after sitting for such a short period.

My 3.2 X300 has sat now for 2 months, started it yesterday, just because, no issues at all. It has 210K kms on it, so not as many as yours. The "old girl" XJ12 V12 has sat for nearly 1 years now, and started just fine over the holiday break, as I wanted to move it in the shed. It is sitting at 489000kms.

The AJ16 is a tough engine, but the wrong engine oil will kill it, as in sludge and excessive carbon on the ring grooves. I run 10W/40 Synthetic in mine, and all the others, except the "old girl" (15W/40 Dino), all year round.

Try some ATF down the holes and let it soak. The small amount of engine oil from the spark plug leak will barey coat the piston tops.

 

I suspect the low compression is due to bore wash rather than stuck rings. This condition is usually induced by shutting down (or stalling) the engine very soon after start up (did you do that when you parked it up?). Excess fuel in the cylinders washes oil off the bores/rings and results in poor compression.

The small amount of oil (think teaspoon) in your approach should do the trick but I would put it in, remove the fuel pump fuse/relay, turn it over a few times with the plugs out, put them back in and start it normally rather than letting it soak.

You may even get away with just flooring the accelerator (turns off injectors on crank), turning over a bit and then releasing the accelerator to start as normal.

Also, I can't imagine any oil would soak past the spark plugs in to the cylinder. Remember that the same seal is holding back 130-150 psi pressure on the other side.

Good Luck

 

Agree with all of the above.

Very unlikely that it is carboned rings. The oil cannot run into the cylinders with the plugs installed.

 

I agree with b1mcp. I have had X300s start then stall and when cranked, it had little to NO compression.
The engine usually starts after cranking for a while but sometimes you need a shot of oil in the bores and then it starts/SMOKES!!!!!!!!!!!!!!!!!!

bob gauff

 

Um, not being picky, BUT, in post #3 it is stated that "a compression tester was hooked up..........."

I assumed from that bit that the plugs were removed, duh, and the oil that was found on coil removal simply ran into the cylinders.

If I missed something, so be it, I will go to the "naughty corner" with my mate, JD, and contemplate something to do with Jaguar.

 

TC-W3 full synthetic two stroke oil.

Once you get it started, add it your gasoline on every fillup at a ratio of 1:500 to 1:640 depending on preference or easiest arithmetic.

One of it's benefits is that it keeps your rings free.

Search TC-W3 here for a few threads, or go to bobistheoilguy for hundreds of threads.

 

Brendan,

Your diagnosis was right on. I think. I did only have the engine running before shutting it down for a couple of minutes. I was moving the car from the drive to the yard to clear a space. Then it sat for about two weeks.

When I next tried to start the car maybe one cylinder would fire. Plus the cranking sounds were different.

The transmission fluid trick worked so it's a done issue. But a lesson learned by me that I will remember.

Thanks for your reply.

Bill Livingston
Hot Springs, Ar.