cel P0304 - Misfire in #4 cylinder
Thank you tibby01, that is one great link
Thanks to everyone else who replied.
I had already replaced plugs, but today got a good jumper lead for the wires, and eliminated them as a cause. I purchased a coil pack, but will check resistance per tibby01's link before installing. If Resistance is OK, I will do a compression test before taking out the injector.
So far, I have invested $15 in new plugs, eliminated wires, and have a sequence of tests available before I start to replacing the more expensive components.
I thank you all very much for your feedback. I am sure to be back to these forums, at least as an observer, for many times to come.
Thanks to everyone else who replied.
I had already replaced plugs, but today got a good jumper lead for the wires, and eliminated them as a cause. I purchased a coil pack, but will check resistance per tibby01's link before installing. If Resistance is OK, I will do a compression test before taking out the injector.
So far, I have invested $15 in new plugs, eliminated wires, and have a sequence of tests available before I start to replacing the more expensive components.
I thank you all very much for your feedback. I am sure to be back to these forums, at least as an observer, for many times to come.
Senior Member

Joined: Mar 2002
Posts: 34,642
Likes: 0
From: Los Lunas, New Mexico, USA.
Vehicle: 2001 Hyundai Tiburon, 2004 Kia Sorento, 2010 Kia Soul
I don't understand how you eliminted the wires.
Have you or do you ever use any fuel injector cleaner?
If not, run, don't walk, down to any local parts store or Walmart and pick up a can of B12 Chemtool. Put it in your tank ASAP. Use one can every 4 tanks. You'll be amazed.
Also, have you changed your fuel filter?
Have you or do you ever use any fuel injector cleaner?
If not, run, don't walk, down to any local parts store or Walmart and pick up a can of B12 Chemtool. Put it in your tank ASAP. Use one can every 4 tanks. You'll be amazed.
Also, have you changed your fuel filter?
Senior Member

Joined: Mar 2002
Posts: 34,642
Likes: 0
From: Los Lunas, New Mexico, USA.
Vehicle: 2001 Hyundai Tiburon, 2004 Kia Sorento, 2010 Kia Soul
That's about how often I use it. Sometimes I'll go to like 6 tanks or so, but I can feel the difference. I stopped trying to use high grade gas years ago, so just one can of this now and then cleans her right up.
WalMart has it for pretty cheap mang.
You can buy it by the case too.
WalMart has it for pretty cheap mang.
You can buy it by the case too.
Hrmm.. Any smoke (black/grey) when you run your car? If so injector probably.. If your injector gets plugged or fails, itll add fuel pressure to the other injectors, making them run richer, giving you black smoke ;/..
Case closed
Culprit - Faulty coil pack.
Sentence - about a half hour of hard labour
Fine - $150 including taxes for coil pack and spark plugs ($Cdn)
How I eliminated the wires? When the delaer sold me the wires and coil pack, the parts guy gave me an old (but still good) wire. Just to be sure, I used the "test" wire on #3 and moved #3 to #4. Reset the CEL, and same code came up. So, on Monday, I will take back the wires.
I am not sure if we get B12 Chemtool in Canada. I'll look it up.
I, in a previous life, worked in a manufacturer of fuel filters. Be very wary of "white box" products and the one with the well known ffffour letter name!
Thanks again for the assistance and especially the link.
Culprit - Faulty coil pack.
Sentence - about a half hour of hard labour
Fine - $150 including taxes for coil pack and spark plugs ($Cdn)
How I eliminated the wires? When the delaer sold me the wires and coil pack, the parts guy gave me an old (but still good) wire. Just to be sure, I used the "test" wire on #3 and moved #3 to #4. Reset the CEL, and same code came up. So, on Monday, I will take back the wires.
I am not sure if we get B12 Chemtool in Canada. I'll look it up.
I, in a previous life, worked in a manufacturer of fuel filters. Be very wary of "white box" products and the one with the well known ffffour letter name!
Thanks again for the assistance and especially the link.
Senior Member

Joined: Oct 2003
Posts: 3,832
Likes: 0
From: Fort Erie, Ontario
Vehicle: 2004 Acura TL
I'm glad you found the problem, I was going to suggest the IM. I warped mine this winter somehow and had the same problem, I heard a hissing or some sort of sucking from under the hood and my CEL was on. I didn't get the code though. I got it machined and it's all good now, but I had the same symtoms, misfires, stalling, not starting.
Anyways glad you found a cure.
Anyways glad you found a cure.



