for about 2 months the engine has been shuttering just a little when ideling at stop lights but not under acceleration or at ant cursing speed. it has gotten progressevly worse and has finely thrown a code P0307 #7 cyl misfire. we bought the car with about 80k on it, it now has 92k. im thinking its time for new plugs.
what brand plug is recommended and do you recommend replacing the coil packs at this time?

 

It's very likely the coil. You could swap them around to see if the fault moves. Beware cheap ones can be useless.

Have the tensioners been updated to the metal-bodied? Search will get you more info but your whole engine is at severe risk if not.

 

thanks for the reply.
I took the spark plug cover off to find the # 7 & 8 where after market coils. when I tried to unbolt #7 to swap it the bolt eye broke. I bought a new one and also pulled the plugs on this side of the motor, they all looked like they had been changed recently and also looked like they where firing ok. put it all back together and took it for a ride. still am getting the #7 misfire fault. im going to run a tank full of gas with seafoam but im at a loss after that.

 

Seafoam will not help nor will any other miracle in a can.

 

ok then
lets work on my assumption of the location of #7 because now im thinking it was wrong. if im standing in front of the car looking at the motor were is #7 at?

 

Standing in front of the car looking at the engine, on pre-face lift cars #7 would be the second from the rear cylinder on the right hand side.

On post face lift cars it would be the rear most cylinder on the left.

 

that would explain it then. thanks once more, ill post the results tomorrow

 

how can you tell pre or post? is it in the vin?

 

The 'easiest' way to tell is if you have a manual or electronic parking brake.

Yours is manual, so pre-face lift.

 

Be sure and listen to JagV8. The tensioners will go bad and will destroy your engine. Please make sure they have been changed to newer metal bodied ones.
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well I had a chance tonight so I glued the bolt eyelet back on the coil I took out and broke off and put it in the RIGHT #7 slot, fixed the problem. for someone who reads all directions for anything I do you would think I would have at least breezed through the manual.
thanks again for the info and I will be looking into the tensioners. I have been told that chains start to make noise at start up when they start to go is this right?

 

Sometimes. Other times the motor goes bang first.

Glad you solved the coil problem.

 

My stype 3.0 had 3 bad coil packs it ran horribly I bought a new set (easier becaude you grt all 6 new plus only taking manifold off once) immediate difference.

Also I put seafoam in my car last week and it's ran horribly since and getting failsafe mode at times, and always use 91 or higher. Anyone had bad experience with seafoam on jags?

 

I still have 1/4 of a tank left of the seafoam mix and have had no ill affects so far

 

It's very unlikely that the Seafoam is causing the problem. This product is nothing more than a few pennies worth of 50% light oil, 30% naptha and 20% isopropyl alcohol. It is VERY effective in doing what it was invented for (unclogging WWII vintage 2 stroke outboard motor carbs) but has little or no purpose on anything else.

 

Could it be bad gas? I've filled up twice at a different station right before this started

 

Filled up again different place and no failsafe codes.. I will personally say I won't be using seafoam in my car again. I'm saying either bad gas or ethanol in premium or the seafoam freaked my car out

 

S-types, like all cars of the era were designed to run on E10, so that wasn't it either.