Good afternoon fellow Jag fanatics,
                                                        Does anyone know what has caused this problem? I changed the 3 spark plugs on the drivers side bank (underneath the intake manifold) a few weeks ago & everything was fine. Yesterday, I changed the 3 plugs on the passenger side. (the easy ones) She ran just fine for around 20 miles, now I'm getting up to 3,000 rpm & she's coughing & spluttering. I can't see why & need your thoughts on this, PLEASE...

Hi Andy --You say its on the easy bank so if it was you I would put the old plugs back in and

if it runs OK again it would mean that one of your new plugs is breaking down under load

[ It does happen at times ??? ]--you can then change them one at a time to find the bad one

and get it exchanged.

 

All the best.

 

Frank

Good advice Frank

Hi Andy --You say its on the easy bank so if it was you I would put the old plugs back in and

if it runs OK again it would mean that one of your new plugs is breaking down under load

[ It does happen at times ??? ]--you can then change them one at a time to find the bad one

and get it exchanged.

 

All the best.

 

Frank

This happened to me about 45 years ago on a A40.  Just because plugs are new doesn't mean they are perfect.  I still have a feeler gauge somewhere!

 

Peter.

Did you change the coil packs as well and did you use oem quality? Gaps on genuine plugs came preset on the ones I just changed on my 3.0 Sport, perhaps you had a dodgy fit or connection somewhere?