P0304 Explained - Cylinder 4 Misfire (Simple Fix)

The FIXD wireless OBD2 scanner and free app for iPhone and Android translates your check engine light into plain English so you can rest easy. In this video, we explain what OBD2 code P0304 means and possible causes.
P0304 means cylinder number 4 is experiencing misfires. A misfire occurs when an insufficient amount of fuel is burning in a cylinder. The efficient burning of fuel is essential to engine operation as the combustion of fuel is what provides the energy to power the engine. A misfire from one or more cylinders can be caused by many reasons from a faulty ignition system, fuel system, or internal engine failure.
When P0304 occurs, it should be fixed immediately as long term driving with engine misfires could cause consequential damage to your engine. Many times, P0304 occurs when there are worn out spark plugs, spark plug wires, or a faulty ignition coil.

0:00 P0304 - Cylinder 4 Misfire
0:40 What is a Misfire?
0:56 Four Stroke Combustion Cycle Explained
1:31 What Causes a Misfire?
1:37 Common Cause of P0304 - Vacuum Leak
1:55 Common Cause of P0304 - Fuel Leak or Congestion
2:20 Common Cause of P0304 - Ignition Coil or Spark Plug
3:35 Other Possible Causes of P0304
4:14 Happy Driving!

#FIXD #P0304 #checkenginelight

[johnrperry]

Finally a car tutorial that doesn't have background sounds burying the speakers voice. Or start with a 5 minute story about how they found out they had a problem.

[stevenshackelford]

This guy needs his OWN You Tube Channel on fixing cars!! This graphical, easy to understand, rational step by step video is a 5 STAR all the way. TY soooo very much!!

[hvacr]

Before you pull the spark plug make sure you blow WITH COMPRESSED AIR, the area around the spark plug so dirt and debris does not fall into the
hole...prep is EVERYTHING

[VIIGerman]

So I bought this old beater sentra, and I got this error, as somebody who is new into the scene of DIY, your video saved me a shop visit and a possible pricey fix when all I had to do was switch 3 and 4, that worked wonderfully, THANK YOU SO MUCH!

[kevinperry]

Also, check your sensor harness wires to see if they are frayed or chewed by rodents. I discovered a chipmunk or squirrel was bringing acorns into my engine and feasting on them and my wiring harnesses. They chewed through the rubber that protects the wires so I'm sure the bare wires were arching and causing the sensors to fail. Just a thought...

[paultavres]

I you had a vacuums leak on intake wouldnt you get a lean mixture code on multiple cylinders
If it was the fuel filter wouldnt all cylinders be miss firing and running lean
Worn spark plug what do they wear on
Most plugs these good are good for 100, 000 miles

[lydiavasquez]

I have a ford van v8 engine. bought 8 coils for little over 100 and spark plugs from oriellys for 6.00 each and 8 fuel injectors from geek parts online for 105.00. Hired a mobile mechanic off of Craigslist who charged me 150.00 in Oxnard. If I was in San Diego I would have drove it across to Mexico where the service would be less.

[truthpower]

Gret advice on testing the ignition coil by swapping it out. It worked! Thanks so much.

[Steve-ogcr]

Careful, you can only swap coils if they are "on plug" coils. If you have a coil pack, do NOT try that.

[JeriGavette]

I bought a 2003 F150 XLT a week ago. I put some gas in it today & some *STP* - *High Mileage - Complete Fuel System Cleaner* in it with the gas. Right after that, I started the truck up & immediately the CHECK ENGINE SOON light came on & it feels like someone had pulled the timing completely out of it!! Its has ran great all week! Is this because of the STP I pit into the gas tank? (It was my 1st thought!) I am a female & just thought I'd start searching what the problem might be, as I am not a mechanic). The guys at the Auto Store recommended I put it in the truck when I put the gas into the tank.
Thanks for this video. Not to find out how many cylinders this truck has!! Ugh...
JG

[alfredweaver]

I have done a complete tune up and I don’t hear any air hissing any where but I still keep getting P0303 & 4. What else could be wrong?

[shannaglosson]

I have a 2019 Kia Optima. I got an oil change, and the next day the check engine light came on and I received a P0304 code. The car is now shaking and idiling rough. I changed the spark plugs, and the coils that didn’t help. The spark plugs were black after only a week of changing them. What does it sound like the problem could be? I’ve read so many things. 9:34 pm

[joedivincenzo]

question, I replaced all plugs and cyl-4 coil, I cleared code ( my scanner said "erase fail"), engine light went out BUT I still have a "pending" P0304 !!! Will that disappear after a

[MrMyreese]

Excellent explanation! I found the video to be very helpful. Thank you!

[froggerraver]

Watching this video got me to subscribe love how you break it down n fixes to a probable solution

[ffas]

Just got the PO 304 Code in my Wife’s 2016 Chevy Malibu 1.5T engine the other morning. I left the car running and opened the hood to do a visual and didn’t notice really anything out of the ordinary until I decided to unscrew the oil cap from the Valve Cover. When I did I could see some blow-by smoke coming out of it at the valve cover with oil cap off. At this point before I do anything I am curious to what you think? I can go in very easily and swap coils with number 3 and 4 cylinder to see if the number 4 coil is bad or not but in the back of my mind is the Blow-by smoke coming from the valve cover. The motor only has 35k miles on it. Can a bad coil cause the blow-by I am seeing? We haven’t driven the car since I scanned the car with my OBD II Scanner Friday morning. It is very early Monday morning right now. I made calls to the GM dealer Friday afternoon where I purchased the car from 6 years ago as a left over in February of 2017 to see if there was any power train warranty left on the car and was told no there wasn’t just in case it is a big problem internally. I have seen another You Tube video a Repair Shop did on another 2016 Malibu with the same 1.5T 4 cyl engine with a PO 301 Code showing Cylinder number 1 with a Misfire they claim has a bad piston. That engine although much louder in the video is also blowing smoke out of the valve cover. I really don’t know what to do at this point in time. In need of some help as to what to do next.

[Kasie.Mckenzie]

Hi I got a question I got a 2010 Honda Odyssey and the code po304 popped up as the four cylinder misfire and I changed the spark plugs I put in fuel cleaner and my vehicle when I accelerate really hard will start to jerk I checked the coils and they look brand new I went to Honda and they said it could be my off brand coils what is going on with my vehicle?

[callaedwards]

totally 'fixd' my car dude. thx

[Gooddaysalways]

I’m happy I found this video. I was totally freakin’ out!

[SwooshSavvy]

Help! I got this code on my v6 mustang and already got new coils, spark plugs and wires and still not fixed . Even did a compression check and switched it around and it keeps coming back as a misfire on cylinder 4. What’s the issue then? Fuel injector? Is that the $700 fix ? ):