Engine misfires when hot....

[Sueatherdesk]

Bought my 1999 S type 3l Jag in July last year with 90k on the clock and not much history, but overall in pretty good nick. However within a short time I  noticed it was missing after driving about fifteen miles.  This gradually got worse - but not on short journeys.  Took it to  the Jaguar dealer Taggarts in Glasgow who charged me a hundred quid to tell me they had it on the machine and nothing was wrong..........  Since then needless to say it has got worse and the engine light has come on intermittently and when revving - the engine is restricted to around 2000 revs.  My local mechanic put it on his diagnostic machine which showed a misfire on no 5 cylinder and the engine restriction - so has changed all the spark plugs replaced the coil on 5 and changed the newer coils on the non-manifold side to the under-the-manifold side!    Unfortunately the fault is back and possibly worse.  Having read other posts, It sound like it might still be the coils.......  However I am wondering if there is anything else that could be the issue that would be worth exploring before we take the manifold off again - and then if we do - is there anything else that should be changed while in there.  Any information

[Old Peter]

Welome to the Club, Sue

I was thinking of the coil but as it has had some attention I would not think it would be my first port of call.

It might be worth checking if it could be the fuel system - injectors?

There could well be other reasons and members with more expertise than me will help.

Regards,

Peter 

[O.T.H]

Hi Sue to me it sounds like fuel starvation so I would say check or change the fuel filters and

make sure all fuel pipes are OK ---That would cause a miss fire and also restricted RPM

I have known a flex fuel pipe to break up inside and cause this sort of problem  .????

Frank



 

[biffer]

7 hours ago, Sueatherdesk said:

so has changed all the spark plugs replaced the coil on 5 and changed the newer coils on the non-manifold side to the under-the-manifold side

 

 Did you only swap your coils over and replace just the 1? it could be as simple if this is so, as another coil pack breaking down.

[Old Peter]

11 hours ago, O.T.H said:

Hi Sue to me it sounds like fuel starvation so I would say check or change the fuel filters and

make sure all fuel pipes are OK ---That would cause a miss fire and also restricted RPM

I have known a flex fuel pipe to break up inside and cause this sort of problem  .????

Frank



 

I had the same problem with a Triumph Herald in 1967, Frank, but it was a bit easier to fix!

Faulty coils do cause a loss of power, but misfires are usually down to a fuel problem.

Peter.