hello all, so I just got back my 06 xj8 from the Jaguar dealer. They fixed the spark plugs, new battery and cleaned the fuel lines. We drove it back and everything was good. Now, we started the car and drove it and the restricted performance light came on along with the check eng. the car was sluggish and we put down the gas and the car would roll and then pick up a bit. I was wondering if the Jaguar dealer messed up their job with the spark plugs and now there is a misfire. Any ideas welcome. In a bit angry cause we just got it back and now we probably have to send it back so they can finish the job this time. Thanks.

 

Well it's hard to say but for sure go back to the dealer and now!

Rather than messed up the job we have to remember that your car is 9+ years old. Stuff will go wrong with it.
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Just had similar issue and found I self caused it as one plug came off a coil pack. Hence no ignition on one cylinder and check engine and restricted performance. You may easily check if all 8 plugs are fully locked in on the coil packs. They are under covers but no screw's need to be removed. Cover on LHS is hard to get out but actually not need to be fully removed to check.

 

We just called Jaguar and they said it is normal for lights to go on after service especially after fixing problems like spark plugs. They said it is not unusual for this to happen. Thankfully, we started the car this morning and no fault lights showed up. No check eng or restricted performance lights came up. Relieved.

 

I've heard this as well, and recall having a similar situation after getting my fuel rails replaced. I'm told it's because the ECU might still think something's wonky. My indy likes to clear the ECU and then drive it a bit before giving it back to see if the codes come back.