Can P0304 damage the catalytic converter?

Yes, if the misfires go on for a while. Unburnt fuel burns inside the converter and overheats it. So do not put off fixing misfires, even if the car still seems to drive well.

P0304 Code: Cylinder 4 Misfire – Meaning & Causes

Q: Can I drive with code P0304?

Not if the check engine light is flashing. Stop when it is safe, because unburnt fuel can destroy the catalytic converter. If the light stays on steadily and the engine runs almost normally, drive gently to a garage.

P0304 code: misfire in cylinder 4

Fault code P0304 means the engine control module has detected misfires in cylinder 4. The mixture in that cylinder does not burn properly, so the engine shakes and loses power. The cause is usually the spark plug or ignition coil for cylinder 4; misfires that go on for a long time can damage the catalytic converter.

Check P0304

When the code is set

The ECM uses the crankshaft position sensor to monitor how smoothly the engine turns. When cylinder 4 misfires, the crankshaft slows for a moment at the point that belongs to that cylinder. When there are too many misfires, the ECM stores P0304; with severe misfires the check engine light flashes.

Can I keep driving?

Have it checked soon

If the check engine light flashes, stop when it is safe and do not drive on: unburnt fuel can destroy the catalytic converter. If the light stays on steadily and the engine runs almost normally, drive gently without hard acceleration and have the car checked as soon as possible. If the engine shakes badly or loses power, it is better to have it taken to a garage.

Symptoms

The check engine light is on or flashing.
The engine shakes, especially at idle.
Jerking and less power when accelerating.
Hard starting.
Higher fuel consumption.

Common causes

A worn or fouled spark plug in cylinder 4.
A faulty ignition coil on cylinder 4.
A clogged or faulty injector on cylinder 4.
An air leak at the cylinder 4 intake port.
Low compression in cylinder 4.

How to find the cause

A mechanic usually works like this:

Read all stored codes and freeze frame data.
Inspect the cylinder 4 spark plug; if the plugs are old, replace them all.
Swap the cylinder 4 coil with a working one from another cylinder, clear the code and read the codes again after a drive.
If the fault stays in cylinder 4, check the injector.
If ignition and fuel are fine, run a compression test.

Other ways the code is written

Scan tools and workshop printouts sometimes show the code with extra characters:

P030400

Related codes

Frequently asked questions

Evoca fault code diagnostics is an informational aid and does not replace a professional inspection of your vehicle. Only an inspection of the vehicle at a workshop can confirm the cause of a fault.

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