Engine light code P0304

P0304 is a diagnostic trouble code (DTC) for a misfire on cylinder 4. This could be caused by a variety of issues, including a faulty spark plug or oxygen sensor. However, a rough idle and a misfire could also be caused by other issues such as a vacuum leak, low fuel pressure, or a malfunctioning fuel injector. It's best to have a professional diagnose the specific cause of the issue.

First you need to retrieve codes from the Engine control module. You can buy a cheap code retriever at harbor freight and get the codes. After you get the codes, if it is P0301 it means cyl #1, P0302 = cyl #2, P0303=cyl 3 and P0304= cyl 4. For ex: if you got P0301 you should remove the ignition coil #1(near the front of the engine, where the pulley is) and change its position with the coil # 2. Also remove the spark plug #1 and change the position with the spark plug #4. Clear the codes and start and run the engine until the check engine light goes on. Check for codes and see if the code change for a different code. If it change the position observe which one is the change. If is P0304 you have a bad spark plug, If it is P0302 you have a bad coil. If it repeat P0301, you have either a low compression, bad injector/connector, bad intake gasket them you should continue your diagnostic. I hope this help you.
Junior.

P0304 Cylinder 4 Misfire Detected,A code P0304 may mean that one or more of the following has happened:

• Faulty spark plug or wire
• Faulty coil (pack)
• Faulty oxygen sensor(s)
• Faulty fuel injector
• Burned exhaust valve
• Faulty catalytic converter(s)
• Running out of fuel
• Poor compression
• Defective computer
• If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs).. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced.

P0304 Code - Cylinder #4 Misfire Detected
A P0304 code means that the the car's computer has detected that one of the engine's cylinders is not firing properly. In this case it's cylinder #4.

Symptoms may include:
* the engine may be harder to start
* the engine may stumble / stumble, and/or hesitate
* other symptoms may also be present

Causes: A code P0304 may mean that one or more of the following has happened:
* Faulty spark plug or wire
* Faulty coil (pack)
* Faulty oxygen sensor(s)
* Faulty fuel injector
* Burned exhaust valve
* Faulty catalytic converter(s)
* Running out of fuel
* Poor compression
* Defective computer

Possible Solutions:
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.


Hope helps.

I have an 2002 Kia sedona the code p0304 means an 4 cylinder misfire and also the wiring and plugs.I noticed an while back that when I press the gas smoke will come from my tailpipe and now my van is hesitating to go and it stumbles and the check engine light is on,I have the same code p0304.

A P0304 OBD2 code is "cylinder #4 misfire detected". The first place to start is your spark plugs. 1. Check condition and for wear. 2. check the spark plug wires or coil packs(depending on which you have).

You have a Misfire at Cylinder #4 meaning:
Dirty, fouled or malfunction Spark Plug at #4 Cylinder. Remove the Spark Plug and check the igntion (spark end).
Ignition (Spark Plug) Wire malfunction for #4 Cylinder.
Misfire from the Coil/Distributor at the #4 connection from Cylinder #4.
Get a Spark Plug/Wire/Coil/Distributor tester and check the Spark Plug, Wire and Coil.
I always recommend changing everything in sets meaning: Change all Spark Plugs and Wires.
Let me know if this helped, or if you have additional information or questions. Feel free to contact me at FixYa.com!

Cylinder 4 is misfiring. Take it to a mechanic and have them take a look at it. Im guessing its the distributor, Spark plug, or spark plug wire on cylinder 4

u have 2 bad coils

Hi

P0304 is actually pointing to a misfire in cylinder 4, not a camshaft sensor problem.

There could well actually be two misfires rather than just one because Ford use a wasted spark ignition system wherein two cylinders are fired at once, one of them on its compression stroke and the other on its exhaust stroke, hence the wasted spark on the exhaust stroke.

You say it is "popping" which would lead me to believe that there is a spark issue rather than a fuel issue, because the popping sound would be the fuel igniting either in the exhaust or the intake rather than the cylinder, and this would be confirmed if you were to run the engine and then switch it off and pull the no.4 spark plug and it were to be covered in fuel.

If you were to find two plugs covered in fuel and the rest ok, then the coil pack feeding those two plugs would probably be the problem.

If only one plug were covered in fuel then either the plug or lead feeding that cylinder owuld probably be the issue.

If none of the plugs are covered in fuel, indicating a fuel problem, and you were to swap the no.4 injector with one of the other injectors, and then the fault code were to change to the cylinder into which you swapped the no.4 injector, then the injector would be the problem.

Very best regards

Geordie