Hi there. We are fairly new to our 2001 s type. At 28k miles new to us it had a slight misfire at idle and at cruising speed 65 on the highway. So first I undertook a permanent windshield seAl which now works perfectly! See my post. We noticed that the more we washed the car the worse the misfire got. Hence I believe tied to moisture. So I bought & NGk pugs. 8 new cop from rock auto. Bought the mid grade cop at 28$ each. NGKplatinum plugs. Replaced all plugs and cops. I pulled the codes prior with a centech reader with no errors. I did notice a fair amount of Rust on each plug, no oil. The plugs were quite pitted but brown in color. I went with the approach to replace all after reading this forum as I don't want engine damage from misfiring and on the cop. Once the covers were off I did not have time to go after the cops and plugs one by one. I also noted that the drivers side cop cover was warped upwards at the aft end near the fire wall. This is where the wires go into the cop. I sealed both of mine with 100% silicone sealant good to 400 degrees. Especially at the back of the covers where the wire goes in. I'll post the plug photos later. No more misfire!!

 

I would not glue down the cover over the coils. You will need access at sometime in the future.

With the age of your car do you know if the tensioners have been changed? It's a big deal with the 4.0L V-8.
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