Since owning this car for over 2 yrs I must say that I am extremely impressed at the quality of Jaguar at that time.

One (1) issue that has been around since I have been driving this car is a misfire code that shows up every now and then on the Engine fault light. I simply plug in my code reader then erase the same two (2) and the light goes off.

I have pulled the connectors off the coil packs and retaped the exposed copper wires due to the (mostly Green wires) heat cracking.

Two (2) days ago the engine light came on again and I pulled the cover off and retaped wires and encapsulated with silicone to try and prevent any arcing that may be occurring.

Short of tearing it completely apart and rewiring each coil pack is it possible that I am looking in the wrong place?

Thanks as always to this forum for the advice

Softball 60/Paul

1989 Mercedes 560SL, 1957 XK 140 Drophead Coupe and everyother British Sports Car know to mankind

 

You might have a couple coils beginning to fail. Common on this motor.

Swap the two suspect coils to two different cylinders. If the misfire code moves to those cylinders, you've confirmed a problem with the coils

Cheers
DD

 

As I mentioned in my initial thread is that the car has been doing this for a couple of years.

The other thing I did not mention is that I still have the same plugs in when I purchased the car.

Softball60/Paul

 

Duly noted.

You might have a coil problem.


By all means, replace 'em. Could very well fix your problem

Cheers
DD

 

Be sure to use the plugs listed in the manual. When I purchased my 95 XJS4.0, 4 years ago the PO installed iridium plugs and it developed misfire codes4 or 5 times on the 400 mile trip home. I took it in to Hennessy Jag ofGwinnett for a pre-purchase inspection (after the fact) and during thecompression check the service manager told me to replace the plugs with the oldcopper core Champion listed in the service bulletin. He and I worked on theinspection together on a Saturday morning, he was very helpful. I had them doall my service work on our Jags until he got transferred when Jag and LandRover combined in one building.

 

Ronald,

When you replaced the plugs with the original specd plugs did it cure the misfire codes?

Thanks

Softball60/Paul

 

See tsb 12-54 spark plug change of specifications AJ16 engine 1995

 

Can these plugs be purchased at any auto parts store? Having difficulty finding the exact part#

Thanks

Softdball60/Paul

 

The correct Champion Part is RC12YCC, but forget the second "c" you won't find it easily. It only denotes a "double copper core" versus a regular copper core. I'm not sure it exists. You want RC12YC if you're looking for Champion.


http://www.sparkplug-crossreference....AMP_PN/RC12YCC


There's a complete cross reference list, including the Champion RC12YC

 

My owners manual calls out RC9YCC Champion Plug

 

Read Post #7, the attachment and you'll find that the spark plug spec was changed in a TSB a long time ago...unless you have a supercharged engine.


It was originally RC9YCC and now its RC12YCC, but you can't find the double copper, so it's now RC12YC.


See this one too:
http://www.jagrepair.com/images/TSB/...rivability.pdf

 

Thanks for your help to all who have responded.

Regards



Softball60/Paul

 

Yes, the excessive misfire codes went away. I have put about 13,000 miles on the RC12YCC plugs ordered through advanced Auto. This year I have purchased the NGK plug, part number BKR5E-11 (V-power)to replace my 3+year old Champion plugs. Can't find the "CC" plug is the main reason for the change, also when I installed mine I used "Never-seez" but did not use the nickel base, which I was told was better. The nickel base helped to maintain the ground on the plug housing for better electrical circuit completion.

 

Well I installed the new plugs. What I saw when I removed the coils packs was mystifying...... several of the plug holes had oil....lots!!!l Plugs did not seem to be very tightly screwed in to the cylinder...but it ran okay

With the new plugs and cleaning out the oil it runs even smoother than before

But the check engine light came on with the same codes..." misfire".

The coil packs look original "Lucas"


There was a fellow on this site who some time ago was making a new harness or harness's??

Is the information on this site... wire, connector, lenghts, etc.

I think when I get time I will make a new harness then replace the coil packs.

Thanks

Softball60/Paul

 

You're probably going to want to change the camcover gasket, make sure you get the ones with the 6 spark plug gasket rings.


Not a tough job at all.

 

I noticed one (1) more thing regarding the plugs. On one (1) of the plugs was a coiled spring just laying on the plug tip. I looked in all of the other coil packs and did not see any other springs. I guessing that this also has something to do with making sure the spark plug and the coil pack have a contact.

Not sure if the coil packs actually inserts over the spark plug cap. I am going to measure to see if there is supposed to be an interference fit.

Any comments are appreciated.

Thanks

Softball60/Paul

 

Update;

1. Installed the new plugs as was discussed in previous threads.
2. Installed new coils
3. Tried to rework the coil wires/plugs...clean, seperated, taped and silicone sealed.

Car runs even smoother than before.......but guess what!!!

I still get exactly the same codes showing up. It seems that this time of the year in Florida is very humid. Don't remember any codes coming up in the Winter.

Is it possible to be any other items.

THE CAT RUNS GREAT!!

Thanks