Hi, im a new owner of a 2004 xj8, beautiful condition, 98k miles. Car sat for almost 8 months with suspension issues before i bought it. I did drain all the fluids including the gas tank, replaced the fuel filter and put fresh gas in before starting it. Im getting multiple misfire codes and/or ignition coil codes and the car is in restrictive mode. The battery is good, the compression is good. I did a smoke test and found no vacumn leaks, the plugs are good, and the coils appear to be almost new, though i dont know for sure. Ive moved them around to see if the codes change at all and nothing. Am i missing something? Does anyone have a wiring diagram and know a way to test the coil wires? Possibly a camshaft sensor? Or is this a common problem with a known solution? It fires right up, but idles rough with obvious misfires. Was hoping to find a direction to go before i just start throwing money into coils and sensors...

 

Other than false air, there is no known problem that causes multiple misfires. Rodents during the sitting period maybe.
The first recommendation is to diagnose the vehicle with generic OBD equipment (by dealer e.g) If that is not accessible I would source an SDD V130 and a Mongoose interface clone.
Misfires are usually due to a mixture that is too lean or too rich, so there must be a few codes. I would exclude the coil too.

SDD is a very useful tool, its abilities are fare more than just reading dtc's.

For WSM or wiring diagram search the jagrepair.com site.

Fritz

 

Mice seem to like the air hoses, & boxes to make nests in.
They also seem to chew on the wires.
Found them often in motorcycles that didn't run well .

 

Could just be a bad coolant temperature sensor/connector.