by Stifull » Mon Nov 25, 2019 8:35 pm
P0304 "Misfire of Cylinder 4" is a result of, and this seems to be the most common order that the culprit is mentioned on Google, Coil, Plug, Injector.... The car shows no sign of loss of power and has been going very well and strong for months since the timing issue was resolved but every 3-4 weeks for 5 - 30 seconds it will idle badly at one set of lights or miss at low revs going up a hill, 5-30 seconds later it's going like a cut snake so I doubt it a compression thing. The Injector shop said it is very common for a "misfiring injector" to occasionally produce a "misfire code P0304" ....The engine is only 50,000ks old and the injs are 170,000ks so it's probably time for a clean.. It makes sense that some small spec has gotten through the fuel filter and is trapped in the small gause screen inside the injector and occasionally it blocks the flow.. Even when they check injectors, they can pass the test BUT... as we found out with our sti, which all tested as "good", having them properly serviced and cleaned fixed the same random intermittent problem that the sti had of a rough idle once every month or two, and the occasional surging, which never returned after the injectors were serviced.. that was over 3 years ago..
Current Subarus
07 Liberty GT (mine) 180kwt on 16lb
98 WRX Club Spes 2 with 2.5ltr upgrade(mine) sub 14 sec
99 Ver 6 Sti also with 2.5ltr upgrade (son) sub 14 sec
02 WRX Bugeye Hatch lots of goodies(wife)
09 Non Turbo Impreza(daughter#4)
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98 GC8 WRX Hatch(daughter#1)
02 Bugeye WRX (daughter#2)