How To Fix P0304 Code For VW Jetta (Meaning, Causes, Symptoms, Diagnosis, Estimated Cost of Repair)

p0304 code vw jetta

Do you know how to fix P0304 code for VW Jetta, Beetle, Gti, Passat, or Tiguan? this is one of the questions our readers ask a lot. Well, we´ve got you covered.

Sometimes it can happen that your check engine light has come on, while your car is exhibiting some other symptoms too.

Things like very smokey exhaust, with a very strong fuel smell coming from it.

But also a very jerky, uneven, idle sound, with a lot of vibrations when your engine is in the low RPM range. This is a situation when you might decide to grab an OBD-II scanner and check things out. With the symptoms like these, you will very likely get the readout of code P0304.

If you have already done so, you might be looking for a solution for this code on your Volkswagen Jetta.

And you have come to the right place because in this post you will find everything you need to know about code P0304 and how to go about fixing it.

Meaning of Code P0304 For VW Jetta

Code P0304 is one of the many standard OBD-II codes, and it is for a cylinder misfire.

These codes, P030 are very easy to read, and they go from P0300 to P0312.

The P0300 means that either more than one cylinder is consistently misfiring, or there is a random misfiring of different cylinders.

Other codes mean that there is a consistent misfiring of a specific cylinder, in the case of P0301 it is the first cylinder, and in the case of P0312, it is the twelfth cylinder.

In the case of P0304, it means that it is the fourth cylinder misfiring.

Misfiring cylinder means that for some reason the fuel is not ignited in that cylinder, on vehicles with catalytic converters this can be a big problem leading to failure of the converter.

P0304 Code VW Jetta, Passat, Tiguan or Beetle >> Check out the video below:

Causes of the Code P0304 On Volkswagen Jetta

In general terms, a misfire can happen due to one of three causes, lack of spark, high amount of fuel, or compression issues.

A spark plug can fail to produce a spark either because it is a culprit, or there are some issues with the ignition coils or wiring.

The bad spark plug can happen because of the natural wear and tear during the exploitation, which puts a finite life span to any spark plug, but also due to deposits on the spark plug.

The presence of excessive amounts of engine oil or coolant in the cylinder during the combustion cycle can create distinctive deposits on the spark plug.

These deposits will also prevent it from generating a proper spark, besides being a sure sign of mechanical problems with your engine.

In case that the fuel injector is stuck open, it will constantly let fuel in the cylinder, which will cause a misfire, but also the improper atomization of the fuel due to a damaged injector nozzle will have the same effect.

Problems with compression are always caused by a leaky intake manifold, which leads to the inability of the engine to draw in the needed amount of air, which automatically produces too rich air-fuel mixture and a misfire.

Read also: Can A Clogged Catalytic Converter Cause A Misfire (Faulty Converter Code)

Symptoms of the Code P0304 On VW Jetta

The first symptom of a misfire, after the check engine light, is the uneven sound of the engine, accompanied by excessive vibrations at low RPMs, for a simple reason that one cylinder is not firing.

The next symptom will be the smell of fuel and smoke coming from the exhaust, though on VW Jetta engine ECM will close the appropriate injector solenoid in an attempt to protect the catalytic converter.

Diagnosis of the Code P0304 On VW Jetta

A quick way to diagnose a misfire on VW Jetta is to swap ignition coils between two cylinders.

In case that either coils or wires are bad, the code will change.

If you had the code P0304 and swapped coils of the 3rd and 4th cylinder, the new code will be P0303.

Otherwise, coils and wires are fine and the issue is somewhere else, and your next step is to check the fuel pressure.

If the pressure builds up and then slowly drops, an injector is stuck wide open and fuel is freely flowing.

If there is consistent fuel pressure, a possible cause is most likely either a bad spark plug or a leaking vacuum.

Estimated Cost of Repair of the code P0304 On VW Jetta

The cost of repairing the misfiring cylinder on a VW Jetta depends first and foremost on the exact cause of it.

But also a big factor is the exact generation of the vehicle, and some seemingly simple repairs can be very expensive on some newer models.

Here is a list of typical ranges, but keep in mind that the actual cost will depend on many factors:

  • Bad spark plug or wires – $150 to $1,800
  • Bad fuel system – $200 to $1,000+ depending on exact issues with fuel system
  • Faulty coil packs – $250 to $850
  • Bad injector – $1,500 to $7,500
  • Vacuum leak – $350 to $1,100

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Jeff is an automotive technician, technical writer, and Managing Editor. He has held a lifelong passion for cars, with a particular interest in cars like the Buick Reatta. Jeff has been creating written and video content about transportation, automotive, electric cars, future vehicles as well as new, used for more than 18 years. Jeff is based in Boulder, Colorado.

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