1996 850 GLT Code P0304

olfac87 · Post by **olfac87** » 26 Sep 2014, 12:30

The check engine light came on today. Local parts store checked the code and it is P0304. Internet research says a misfire. I replaced the plugs one year ago, I believe with Volvo plugs (need to check as I didn't write it down). Does 0304 mean cylinder #4? (My insinuation from reading other posts.) I just recently cleared code p0422 by replacing the cat (2 months ago). And I installed a new fuel filter about a month ago.

I have no history of my replacing the cap, rotor or plug wires in the last 80k+ miles. (Car now has 134k.)

Not sure where to start with the troubleshooting - any suggestions would be great.

Post by **rmmagow** » 26 Sep 2014, 13:05

Did you use Volvo plugs? Run a compression test or just do a full plugs, wires (Bougicord) Cap and rotor (Bosch). And ONLY Volvo plugs.

olfac87 · Post by **olfac87** » 26 Sep 2014, 13:09

rmmagow - I need to pull a plug to see what I used. I currently have Bougicord wires on and a Bosch rotor. Can't tell how old and am looking through my records to see if I missed recording any replacements on my master service history list. For a compression test, I assume that requires special equipment or a mechanic? (I am a novice car tinkerer.)

Post by **rspi** » 26 Sep 2014, 15:27

olfac87 · Post by **olfac87** » 26 Sep 2014, 16:31

That was a really helpful video. Looks like a series of tests I can do at home. Thanks for posting it.

olfac87 · Post by **olfac87** » 05 Oct 2014, 09:55

rmmagow wrote:Did you use Volvo plugs? Run a compression test or just do a full plugs, wires (Bougicord) Cap and rotor (Bosch). And ONLY Volvo plugs.

I finally worked on the car today. The old plugs were Bosch Platinum. Even though they were 1 year/7k miles old, I replaced them with Volvo plugs along with a new Bosch distributor and rotor, Bougicord plug wires and Mann air filter. The car works so far. The check engine light is still on - I presume I need to reset it with the code reader?

Post by **erikv11** » 05 Oct 2014, 20:33

Other people have had issues with those Bosch platinum plugs, that could have been why #4 misfired. Regardless, those new ignition components will work great. If something does pop up you will know not to blame them.

Yes you have it, the CEL must be reset. You can also unhook the battery if you want to, that is another (a bit more dramatic) way to clear the codes.