Code PO304

calvinlai · 03-02-2006, 06:52 PM

Hi,
I own a 2002 WRX, mileage is 62000. The Check Engine Light came on last week while I was driving on highway. I can feel it was hestiating on light throttle, but felt fine on full throttle. I pulled the code from my PDA code reader, code PO304 was indicated - misfire in cylinder #4.
I replaced the coil pack in cylinder#4, cleared the code. CEL came back on while I test drove it. I then replaced all 4 spark plugs today, cleared the code, CEL came back on again.
I gave up and took it to a Subaru dealer. First thing they told me was that I need to replace my coil, then I told them I've already done that.
I asked them to reflash the ECU, they tried but failed, they claimed they tried but "the car won't take it" - whatever that means. They also claimed that they called SOA and SOA claimed everything is up to date and the ECU won't take the reflash. My question is I bought the car new in 2001, haven't had it reflashed nor had any upgrades done. Why on earth would they say it is already up to date? Have Subaru not updated the "programming" in the past 4+ years?
In the end, they said my WRX needs a new Injector for cylinder #4. I paid my service charge and left.
Can someone please give me some advice on what can I do? I have been a mechanic for 15 years and have not seen any injectors gone bad (on Foreign cars).

Thanks in advance for the help.

GetUpInDer · 03-03-2006, 10:16 AM

I have been a mechanic for 15 years and have not seen any injectors gone bad (on Foreign cars).

Thanks in advance for the help.[/quote]

It's pretty rare for injectors to go out. The subaru coil packs do go bad often, I've replaced a number of them but never an injector.

bigbadbuddha · 03-03-2006, 12:08 PM

Quote:

Originally Posted by calvinlai

Hi,
I own a 2002 WRX, mileage is 62000. The Check Engine Light came on last week while I was driving on highway. I can feel it was hestiating on light throttle, but felt fine on full throttle. I pulled the code from my PDA code reader, code PO304 was indicated - misfire in cylinder #4.
I replaced the coil pack in cylinder#4, cleared the code. CEL came back on while I test drove it. I then replaced all 4 spark plugs today, cleared the code, CEL came back on again.
I gave up and took it to a Subaru dealer. First thing they told me was that I need to replace my coil, then I told them I've already done that.
I asked them to reflash the ECU, they tried but failed, they claimed they tried but "the car won't take it" - whatever that means. They also claimed that they called SOA and SOA claimed everything is up to date and the ECU won't take the reflash. My question is I bought the car new in 2001, haven't had it reflashed nor had any upgrades done. Why on earth would they say it is already up to date? Have Subaru not updated the "programming" in the past 4+ years?
In the end, they said my WRX needs a new Injector for cylinder #4. I paid my service charge and left.
Can someone please give me some advice on what can I do? I have been a mechanic for 15 years and have not seen any injectors gone bad (on Foreign cars).

Thanks in advance for the help.

I had the same problem with my coil pack on cylinder 4. It popped off one day. I wnet down to my mechanic and had it replaced. When i got it back it was still hesitating. Turns out that it wasn't sealing properly. he took some sealant and went around the pack and viola.... problem fixed.

calvinlai · 03-03-2006, 07:20 PM

Thanks for the input.
I swapped the injectors in cylinder 2 & 4 today. Ran engine and this time I got Code 302 (misfire in cylinder 2). Googled and found injector for only $80 so I ordered one. Hope this will fix the problem or my wife will kill me...

unisaw · 06-23-2008, 03:35 PM

I had the same problem on a 03 Nissan Sentra ( PO304 / Cylinder #4 missfire )...I have changed the Spark plugs and, so far, it's doing OK... Check engine light went off...for how long??? If someone ran into the same situation and know what will come soon, please, let me know...¸Tks.