Hello, my friend has a 2003 xj8 (American drivers side) and I’m helping him try and diagnose and fix an issue (we don’t know the most about cars but we are learning). About a month ago it would start to go into rough idle and limp mode. And it read P0303. We looked it up and replaced the 3rd ignition coil (from what we could find online it was the 2nd one from the front on the left). The issue still persisted after this. We check again and the same error code. We are thinking it might be an electrical issue now and we are going to have to replace the connector. We just wanted some more informed opinions on what we should do.

 

Wrong coil.
This pic has been displayed on this forum for years.
See the actual coil/cylinder layout for the 4.0

 

Another example of confusing Jag docs: on the X308s, 303 is third back on right side -- as Bob noted. I guess the confusion rests with the fact that in the UK, 2003 models are 350s.

 

X350 in uk started at 2003.5. In usa 2004.