I have 2001 XK8 not XKR. It has 93,000 miles. I have a situation were the check engine light comes on, usually after a rain shower. The codes are P0305,0307,0300,0302,0304,0306,0308, 0301, 0303. Summary: all Cylinders say Misfire Detected. Sometimes I can feel a shutter in the engine for a moment. Other times nothing. The car drives great, engine is smooth. It has had all the coils and plugs replaced. It has never happened when my mechanic has had the car. I can reset the codes and drive for weeks, no problem. Then it will light up again. My guess is that it is in the ECU/ECM. Possibly a cold solder or something. I don't really want to open it up.

Has anyone had a similar experience?

Thanks in advance.

 

Could be moisture getting into the throttle body....

 

Or a knock sensor?

 

I'm looking at the ED for the 2004 4.2, apologies... And for the life of me (I don't think it listed) I cannot find the ground location PIS13 listed in the diagram. I think it's missing.

Anyways,
I'm thinking there might and must be something similar in the 2001. I have a NA 2002, but am at work and don't have access to the 2001/02 diagram. Maybe the same, maybe different.

That's a LOT of codes which leads me to a grounding idea OR,,, what plugs and coils did you use?

 

Thanks for the input so far. They give me additional places to look. I will have to check the brand on coils and plugs.

 

No worries. This is from the 2000my ED...
​​​​​There is an ignition relay. See below. Maybe swap it out with a known good relay, maybe horn or something, and take her around and see if she plays up...?

Was this happening before the coils and plugs were changed. It's an important point. Anyroads,,,,

I'm sorry. Maybe someone with more experience than me will help. I am having a hard time using the FIG 4.3 diagram key to give a description of where the ground points for the ignition coils (image below) are located... Hopefully someone else will fill in my blanks. Maybe all of that is only grounded within the ecm...?

 

Here. Try these and match them up with the grounds in the image above.