ej25 sohc flashing cel

[scoobysnack227]

i have gone thru sensors as well as all the normal for a p304 cyl 4 misfire obd code (i.e changed plugs, wires, coil pack as well as compression and its solid on all 4. i have a 2001 obw manual with an ej25 sohc that will only flash if idling amd i have tested this plenty, over 3 weeks with no cel flash just stays on by keeping rpms over 1k when at stops. she drives fine with no significant notice from a misfire, only notice my mpgs have dropped to about 22 hwy when before was closer to 28 mpg hwy. i have ruled out my fuel pump as it shoild cause a p300 random misfire and my injectors seem to be flowing fine. any ideas for this would be great as im considering a possible rebuild or jdm swap but money is tight right now so im trying to see if she can be back without drastic measures. and by the way the head gaskets have been replaced,

thanks

[Fairtax4me]

Have you checked fuel pressure with a guage? The 00-04 models have problems with a cap on the pump bleeding fuel back into the tank.

 

Check to make sure the #4 injector is clicking with a stethoscope.

Also you could swap injectors 2-4 and see if the code moves with the injector.

[scoobysnack227]

didn't check with a stethoscope just an ohm meter also it was buzzing so i moved on but i will try and move the injectors and see if they follow

[Caboobaroo]

How long ago were the head gaskets replaced? What brand of parts were used? Was a valve job or adjustment done at that point in time?

[scoobysnack227]

I bought it used from someone who replaced the head gasket's cam seals etc. but I don't believe the valve was done at all .... also I know it's due for another timing belt change at this mileage 200k