hi i was wondering if any of you could offer me some advice . i have a 3.0 ltr v6 s type . its done 75,000 miles with full jag service history . the engine management light recently came on so took it too a local garage my hubby uses for them to do diagnostics . came back that number 6 cylinder had an intermittent fault . the mechanic said that it was more than likely a spark plug . so i got out my service history too find it had had a major service at 70,000 miles that should have included a full plug change .the mechanic at the garage has said they probably hadnt changed the last 2 plugs due to the location of them . is there anyway i could tell if they had been changed ? this was a main dealer full service that cost me almost 600 qwid . thanks for any info you may provide

 

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I don't know this engine but would guess the answer will be 'take the plugs out'.
Worth buying yourself a cheap OBD code reader - you'll need it!

 

Far more likely it's a coil that's failed. On these engines it's hardly ever a plug (which you'll probably find WAS changed).

 

OK, so does he change the coil to see if the fault moves?

 

PLugs are rated for 100K of service. They were changed out at 70K miles - could possibly be you have a cracked ceramic insulator (but I highly doubt it, especially with the dealer installing them - they do this stuff for a living) - +1 above on the coil. That's where I would start. You can move the coil to another cylinder to see if the fault "follows" as mentioned above - I have also heard mention of IMT O-Rings as well.

PS - Your "mechanic" guy doesn't seem to know Jags based on his "plug" theory...be careful...

 

Do you also get the oil leak into the plug well problem with these engines?

 

Good point steveinfrance! - if you find any oil residue on the coil when you pull it out you must get the cam gasket and spark well gaskets changed out or risk repeated coil issues.

 

Plugs are 70K on the 3.0.

I still reckon the odds are it's the coil. Swap it for another to see if the fault moves if you like.

 

Oops...my bad - thinking 4.0 always...