So I've been fighting this misfire on my 2000 XJ for some time now since I replaced the head (not sure how it ran before), recently it's thrown a P204, P201, P205 (injector circuit malfunctions on cylinder 4, 1 and 5) and P300 (all cylinders misfire) and P301/305 misfires)

It'll run pretty decent, but after about 10 or 15 minutes of driving the CEL will flash and it'll go in to limp mode

These are the only codes poppin up.

Thing was, at first it threw a 305 code for cylinder 5 misfire, i checked the voltage and the injector wire was firing, checked injector ohms, and it ohmed out fine. so i swapped 1 and 5 injectors after attempting to clean the one that was in 5 and it seemed to help (before it wasnt getting any gas at all through that injector bc i could remove the injector plug and it wouldnt change idle). now that the injector is in cylinder 1, i can remove the wire and itll make it idle rough, same with the swapped injector in number 5.. so i can verify that the wire is firing.

I'm lost.

 

Sorry, i don't know about the injector codes, but i'd check the coil(s) for the misfire codes.
*Cause you said it threw a 305 code for cylinder 5 misfire, and you started checking injectors? Misfire points to coil, not injector.

 

how do you figure? you can have all the spark you want, but with no fuel... whats that going to get you?... a misfire. misfire can come from either lack of spark, lack of fuel, CPS misalighment, IAC, low compression, blahblahblah. if the computer detects a misfire from any of these things it will throw a code. i'm sure my issue lies in the injector circuit somewhere

i already checked the coil weeks ago, it's firing on cylinder 5, i had it ruled down to what i thought was a clogged injector (covered this in my build thread and another tech question thread a few weeks back)... so thats what lead me to swapping injectors around.

 

I would suspect that you either have a bunch of faulty fuel injectors, or possibly a problem internal to the computer which drives the show......