I have a 2009 malibu I am getting a code p0304 cylinder misfire. What is the most common problem with these cars with this code ?

Dear Earl,
You have not supplied me with the year, make, or model of the vehicle, but for the past (about 20) years, the most common answer to your problem in the USA would be a bad "coil pack".
This is usually a tall skinny plastic thing that makes the spark for the spark plug, and has a wire connection on the bottom to energize it.
The top of it has either a hole for the spark plug wire, or a wire that goes to the spark plug.
The number of coil packs are according to the number of cylinders/spark plugs in the engine. ( Usually 4 or 6.)
God bless your efforts.

Needs a cat and need to check the injector and coil. Coil most common on that model

P0300 = Random/multiple cylinder(s) - misfire detected.
P0302 = Cylinder 2 - misfire detected.
P0304 = Cylinder 4 - misfire detected.
P0306 = Cylinder 6 - misfire detected.

A misfire can be caused by a few things. The most common causes are usually spark supply or fuel supply. Get BOTH of these checked.
All the misfires are on the same side of the engine so I would suspect a fuel rail or an injector issue on that side of the engine.

You'll have to get someone to check the spark and injector on cylinders 3 and 4.
Code 303 is for loss of power on cylinder 3 and code 304 is the same for cylinder 4. The most common causes are lack of spark or fuel.
Once the problems are fixed the codes will need to be erased with a scanner or code reader.

CK codes c0131 ABS/TCS system pressure circuit malfunction. Their is a Technical Service Bulletin out for this that is being addressed by chevy so you may want to get in touch with them.

p0304
cylinder no.4 misfire detected

p0316
misfire detected during startup -first 1000 revolulations

Code P1399 is specific to Honda - it is an error code for "multiple variable misfires detected". P0301-P0304 are common OBDC codes for all cars, specifically "misfire in cylinder X".

You will get the P0301-P0304 codes on your OBDC reader when you plug it in (if actually errors), but will only find the P1399 if you select Honda as the manufacturer.

Just got these errors today on my CRV 2000. Now I have to figure out what is causing two of the cylinders to misfire.

p0304 means the computer has detected that cylinder 4 is misfiring. the most common cause of a misfire is a faulty spark plug or plug wire. depending on how long its been since a tune-up, they could just be worn out. you can look at where the plug wire snaps onto ignition coil to see if the coil tower is corroded, also another cause. other causes of misfire in one cylinder could be a faulty fuel injector or low compression on that cylinder. but ignition is the most common

u have 2 bad coils

Here is a good site for OBD II trouble codes.  P0300: Random/Multiple Cylinder Misfires Detected, P0301: Cylinder 1 Misfire Detected, P0304: Cylinder 4 Misfire Detected.