P0300 random/multiple engine misfire code

i have a 2001 v70 about 300,000 kilometres on it.
the engine keeps misfiring and pull the code p0300.
it a non-turbo
i have changed the following
plug coils
fuel pump
map & maf sensors
o2 sensor bank 1 sensor 1
air filter
spark plugs
engine temp sensor
fuel nozzles
throttle body and had the cylinder removed to clean the valves and have the same code.

so recently i removed all nozzles together with the fuel ray from the intake manifold leaving it exposed and crank the engine.
at initial crank, all nozzles sprayed and with continuous cranking, only nozzle 2,4 & 5 sprayed.

 

check the wire harness to the injectors for any cracked connectors, you should be able to use a test lamp to see if the injector is getting a pulse. Also see if you can find a service that will clean the injectors (or see if you can find an ultrasonic cleaner). What happens if you swap position of the nozzles?

 

Thanks. Nozzles 4 & 5 were swapped with 1&3, still the same result.

 

so if your injectors don't fire in the same positions after the swap, then that tells me they are not getting a signal from the ECU. Sounds like a wiring or connector issue to me. You may want to try pulling out the ECU, cleaning the connectors to the ECU with some electronics cleaner then checking for continuity to the injector connections. Are there any check engine fault codes? I'd think that an open circuit to the injector would throw a code. After that, I'd check for fuel pressure at the rail and finally check compression.