Hi guys, my 02 Jaguar 4.0 keeps reading misfire on 1, 7 and 8. Here lies the problem, I’ve changed all the plugs to Bosch Platinum, checked all of the coils. All seem fine, she fires right up, idles and revs just fine. Wouldn’t she sound really rough if all those cylinders were misfiring? Could the problem be low fuel pressure under load?
Please help...
Thank you, Alan

 

Enough misfires to flag codes may be undetectable to a person.

The codes PDF is a free download off the site with the workshop manual or on JagRepair.com - Jaguar Repair Information Resource and gives a list of the possible causes for each code. (One of the quite long list is fuel but do not ignore the others.)

You might try swapping a coil from a cylinder that gets flagged with one that isn't and see if the code moves.

 

I am assuming that what you are referring to as "misfires" are OBD-II misfire codes...

These codes arise when the engine management system detects a cylinder firing with less force than the others; this can be caused by coil-packs, bad/dirty/worn injectors, etc. I would think that if low fuel pressure is the issue, then more/all of the cylinders would be impacted.

You might want to check your fuel pressure via the schrader valve on the fuel rail and have a look at the injectors on numbers 1, 7 and 8.

 

Invest in a COP tester and ensure the fuel injector harness plugs for affected cylinders are fully seated...

 

So we can assume you are seeing P0301 P0307 and P0308? Moving coils is an easy way to isolate an ignition from a fueling problem. As S-Type Owner posted..Chances are you would have a P0300 if all the cylinders were effected.