So I replaced the spark plugs, distributor cap and rotor on my '92 Sovereign when I first got the car. It definitely helped smooth out the idle and gave the car more power on the highway, most noticeably, passing power above 65MPH.

While the plugs helped, there is still a miss at idle I'd like to figure out. I've checked the resistance on the wires, and all pass except the coil wire, which is reading 4.7k ohms. The range is 1.8 - 4.1k ohms for that wire. I will be replacing the set. They are the original Lucas wires.

When I removed the plugs, I was really surprised to see how bad they were. Lots and lots of ash buildup, and at least one was very wet with oil. The car does burn a bit of oil on start-up, just a second or two of blue smoke. There was about 1/2" of oil in every well except cylinder 1 which was bone dry.

I've taken the pictures of the plugs that I've replaced, and took note of their respective cylinder. The plugs were installed April 1999 at the dealership, and were in the car for 14 years and 18,500 miles.

These are their stories (DUN DUN):

Cylinder 1:


Cylinder 2:



Cylinder 3:



Cylinder 4:



Cylinder 5:



Cylinder 6:



-Nick

 

LOL I'd say they might be expended

 

NTL

Not that you asked, but I thought I would share me experience on this matter. I discovered oil in my plug cylinders last fall and set out to change the cam cover gasket and boss plug gaskets (these are why you have oil in the cylinders). What should have been simple, turned out to have complications. I hope yours turns out with no problems, but better to be prepared than not.......

Instead of retyping everything, go to this link and read the thread:

JagFORUM Logon

Below is another thread with the Jaguar part numbers listed for you convenience: (for changing the cam cover gasket)

JagFORUM Logon

 

Thanks for the reply Rob. Those links may come in handy. The dealer replaced a few valves, along with the head gasket, head bolts, and valve cover gasket when the plugs were changed in 1999. ($2,600 bill!)

Any thoughts on the condition of the plugs and maybe a cause would be appreciated. The more I can learn about the car, the better.

Thanks,
Nick

 

Looks like moisture from a car not driven until warm and stored without any lube or storage oil put in cylinders, otherwise normal for a rarely driven car that sits a lot with no maintenance.

 

Nick,

If I recall the history correctly, I think your vehicle was driven very little over the span of a dozen years, so possibly the boss seals deteriorated due to lack of use. Or the dealer simply put too much torque on the cam cover screws and compromised the boss seals.

In regard to what appears to be oil on the tip of the plugs, I venture to guess there is one or more valve seals that have deteriorated as well....... maybe. I have no experience with removing the head and replacing seals, so I'll give no advice as to that process.

What I would do is monitor those new plugs for a few weeks (assuming you replace the boss seals, plugs and cam cover seal) and pull them every couple of weeks to see if the problem clears. It may be just a case of the oil seeping down the threads from the compromised boss seals. If so, there probably isn't and issue with valve seals.

The ash build up is another indicator of the oil being burned. I would again recommend the replacement of the cam cover seal, plugs and boss seals to eliminate the induction of oil via the boss seals.

Good luck.

BTW, replacing the cam cover seals is probably a $30 or $50 (good quality parts) dollar job and will take an hour if all goes smoothly, a lot less expensive than going to dealer and having them talk you into digging into the valves. Eliminate the boss seals as the problem.

 

I would do a compression test on all the cylinders just to see what compression readings you get. At least that way you will have an idea if there is if there is a problem if any of the readings are not consistent with the other cylinders. The buildup on the plugs seems very excessive for that mileage. Do you have to add antifreeze periodically or is the coolant always at the same level-ie you don't add any at all. Cary

 

Thanks for the reply. That's not a bad idea. I have had to add a very small amount of antifreeze, about a cup it two due to seepage from the plastic expansion tank at the seam and loose hose connections.


Compression testers are cheap enough so it's probably not a bad idea to buy one and just see where I'm at.


Thanks,
Nick