So I was driving my 96 XJS, with the six, over to Opening Day when the car started shuddering at speed. Eventually the Check Engine light came on and started to blink.

I was about 10 miles from home, and I managed to get it there to pull the codes.

I pulled the following codes:
P0301
P0305
P0306
P1314

Wow. I wasn't expecting to lose 3 coils at the same time!

I reset the Check Engine light at this time the only codes that came back was P0305 and P1314.

I will replace the coil today at Cylinder #5, but I'm concerned that I may have a larger problem looming? I only own 2 new coils (yes, made in Japan), is it plausible for one failed cylinder to screw up the others?

Thanks for any help.

 

Unusual to lose 3 coils at the same time but possible I guess? You might want to look at your cat on bank 2.

Do you lose power at higher speeds say over 30-40 mph? Does the car idle ok?

A blocked or melted cat would give you these symptoms and definitely cause misfiring. Your cat would get red hot too.

 

I did notice that the shudder would occur when cruising at 52mph. Bringing it down caused the shuddering to go away (initially)

When the problem got worse, downshifting helped...but only temporarily.

How would I diagnose the cat? I guess I naturally assumed it was a coil.

The temp gauge never showed anything running hot...but I don't suppose that it would.

Thanks for the help.

 

You can try banging on the cats with a rubber mallet. If you hear anything rattling around that's a bad sign. Also you can try to measure the temperature before and after the cat with an IR gauge. A drop in temp is a bad sign. You can also drop the cats and look inside to see if the honeycomb structure has broken up or melted.

Probably the most definitive way is to remove the upstream O2 sensor and screw in an exhaust pressure sensor to measure back pressure. Any good exhaust place should be able to do that for you if you don't have the bits. If you have more than about 1psi at idle that would indicate a blocked cat.

 

Good tip to try the mallet test, if it rattles it's broke.
I had the same on my Subaru which started off well and then completely ran out of steam once you were up to speed; the broken cat blocks the exhaust outlet and back pressures into the engine causing it to choke to death.
Mechanic cut out the casing, removed the broken bits and welded the plate back on.
The car runs fine after and it will do until the next MOT or it is death by scrapyard.

 

Cats aren't rattling.

I know thats not 100% proof, but its a start.

Were the OEM cats made by Walker, cause that's whats there.

I'm going to swap coils and see if the problem moves along with it. Coil #3 had no issues, so I'll move it over there.

 

Well there's yer problem.

The rubber boot on the coil exploded.

When I took off the plastic coil cover (with the Jaguar logo), I saw oil. There is visible oil on coil #5 and #6, although I believe it came from #5.

Wonder what caused that? I wonder if the coil is still good?

Should I go in there and replace the spark plug too?

 

I think 'Bosal' was the OEM.

I was just under the car a few days ago and recall seeing that name stamped on the exhaust. Can't remember if it was stamped on the mufflers, the cat converters, or both.

Cheers
DD

 

Well now I know what happened.

The spark plug blew. The one in #5 is destroyed. Never had that happen to me before.

That explains everything. Oil was easily bypassing the chamber and leaching into other cylinders. Any harm in draining the oil into the cylinders by loosening each of the plugs? Theres only broken bits of plug in Cylinder #5.

I guess the engine would be shot if there was any real collateral damage?

 

It sure did ! Burn-thru is common enough but, FWIW, this is the first one I've seen 'exploded' like that




Spark plug well seals leaking





I dunno. Probably is. I presume you are gonna replace just the boot?




Did you pull the plug out? How does it look?

Cheers
DD

 

Yikes

Are you saying there are bits of the broken spark plug *actually inside* the cylinder?

Cheers
DD

 

Well the ceramic must have gone somewhere.

I suspect it went it the chamber. There's some ceramic left, but not much...

 

Crikey Vee!! Not seen that before! Can't imagine that ceramic in the cylinder is a good thing

Hopefully it was just a faulty plug and the ceramic bits were tiny enough to pass through the engine. Careful inspection would seem to be the order of the day!!

 

Sorry about your problem.

I have never heard of this on any AJ16 engine.

Had you replaced the plugs recently? Did this suddenly happen when hitting the gas?

I hope no damage has happened

 

I changed the plugs about 10,000 miles ago, which was about a year ago.

Can't tell exactly when it happened, but I don't drive the car severely, so I just think it was a manufacturing defect.

I'm going to replace the coil boot and see if the thing doesn't work normally again. No need to dip into my cache of expensive japanese coils if I can avoid it.

Thanks for the help and advice!

 

Boot was replaced, keeping the same pack.

All plugs were replaced to get the oil out of the wells...and into the cylinders unfortunately. (there's got to be some benefit to using $2 plugs! Replacing them was less work than cleaning the oiled set)

All of the plug electrodes were dry. Whatever caused the oil seepage happened from the outside. (Except for the shattered plug #5)

The car started up and runs normal again. I'm glad I did not have to use a spare coil.

I am going to buy a few more rubber boots though. NAPA sells Belden branded boot covers for $21 a piece. (Part #702478)

 

Glad it all worked out. I was getting stressed out on your behalf for those ceramic parts in the cylinder!!!

What king of plugs did you use??

 

Sticking with Champion 71. (RC12YC)

I shoved a vacuum into each cylinder when changing plugs, but I didn't hear anything get sucked in.

I think what happened is this:

A few months ago, I was driving up I-95 for about 3 hours when I noted smoke in the rear view mirror. I pulled over and opened the hood. I was losing oil from the rear of the engine block. That oil that was dripping out was steaming on the engine block causing the smoke.

The cause of that was loose bolts. When I replaced the camcover gasket, I tightened it back to spec, using a torque wrench, but it felt too light, but I followed it anyways.

Apparently it was indeed too loose. I re-tightened all the screws by hand this time. I didn't crank down too hard, but I got them all home nice and snug. (Rear screws were looser than the front ones)

Anyways, I'll bet you that I had oil in the cylinders since then and eventually I cooked one of the spark plugs long enough.

That's what I suspect happened.

 

I completely understand about the cam cover.

Following a series of failed attempts to end the leaks with first my original cam cover and new gaskets, and then with a used cam cover with yet another new gasket, I finally found someone selling New Old Stock cam covers and some OEM gaskets. Imagine my dismay when my brand new cam cover followed on the path of its two predecessors!!!

All it took was a manual half turn on all the screw using the Jaguar specified sequence::



After that not only does my new cam cover make the engine bay look nice and new, but also leaks no oil!!