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Misfiring 1996 Jaguar Vanden Plas

I own a 1996 Jaguar Vanden Plas 6 cyl. Living in Minnesota, I only drive the car in warm weather and usually accumulate only about 3000 m annually. Being an old car, it’s developed some nuisance oil leaks which I think I’ve traced to the intake manefolds. Small leaks, but noticeable in the garage. My question has to do with the firing of the cylinders. Several years ago, the check engine light came on. Upon checking it read #6 cyl random misfire with catylitic converter malfunction. I think I changed the coil, fuel injector and spark plug on #6. The problem resurfaced some time later with codes reading randome misfires on # 1 and # 6. Now the problem is back again, but worse. After driving for about a hour, the engine spontaneously shuts off when I slow down at a corner or stop. Doesn’t do it all the time. I thought it might be fuel, but codes read random misfires on #6 again.

Any suggestions.

Being a Jaguar it has developed some oil leaks… Fixed it for you!

Intake manifolds don’t generally hold oil… so I don’t think that is it. I suspect valve cover gaskets.

You drive it 3000 miles a year… how many miles does it have now? How often do you change the oil? does it use oil?

Have you ever changed these 24 year old spark plugs and wires? Or just #6? I’d suggest a mechanic ride with you with his scanner so he can look and see the data when this happens.

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Which day does warm weather occur in Minnesota? (I’ve forgotten, but I seem to think it was one day in mid-July)

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You should check the compression in all cylinders and see if there is a difference in them. Also, while it’s a completely different engine the technology is similar … my 2002 Mazda Miata developed a misfire on cylinder 4, and after trying everything else what fixed it was adjusting the valve lash. These engines use a shim to set the gap between the valve and the cam lobe, and over time you may need to replace the shims to maintain the correct gap.

I think it is the fourth so the fire work’s can help with the heat.