P0304 Error (Cylinder 4 misfire detected)

oakleyh · Post by **oakleyh** » Sun Jun 17, 2007 7:58 pm

Hello,

I purchased a 2003 Jetta TDI yesterday and on the way home the check engine light came on. The fault was P0304 (Cylinder 4 misfire detected). I ran some injector cleaner through it and reset the fault and it has not came back on? What causes this fault and did I do anything by putting in the injector cleaner?

Thanks Kris

CoolAirVw · Post by **CoolAirVw** » Wed Jul 04, 2007 9:07 pm

My answer is very generic. Forgive me if I'm stating the obvious.

If the code doesn't come back on then dont worry, be happy

. It may come back on with a few drive cycles.

304 means cylinder 4 is misfiring although sometimes it can be a different cylinder or mutiple cylinders misfiring and the computer "mis-identifies" it for some reason.

If we assume its number 4 you can switch injectors from 1-4 and then see if the 304 reoccurs its not the injector. If code 301 triggers it is the injector.

If 304 does reoccur I would compression check cylinder #4 (cracked valves or low compression??? )

Lets not forget the obvious, air in fuel, clogged fuel filter, bad fuel, homebrew bio ect.

I guess I should ask the obvious, does your motor feel like it has a miss?

oakleyh · Post by **oakleyh** » Fri Jul 06, 2007 3:54 pm

Richard,

Thanks for the reply and information. Yes it did feel like it was missing when the fault occurred. It has not came back on since I ran the injector cleaner through it, I have put on three thousand miles and no light.

Can you tell me is OK to run my 03 with 505.01 oil. Everything that I read says to use 505.00 but the dealer sold me 505.01?

Thanks Kris

CoolAirVw · Post by **CoolAirVw** » Sat Jul 14, 2007 11:52 am

You got me thinking and reading and researching. I dont have your answer but I do have a recommendation. Try the Elf oil.

Expensive but there are claims of 4mpg increase. Even if its only 1 mpg increase it will pay for itself. You can buy it here. Plan ahead, buy enough to get free shipping. You'll use it eventually.
http://www.tdiparts.com/catalog/index.p ... rers_id=60

Here's a informative thread on oil. Try to read all the posts and all the links.

http://forums.tdiclub.com/showthread.ph ... ght=505.01