Subaru Error Code P0304: How to Fix It

Q: Can I drive my Subaru with P0304 error code?

You should avoid driving with a P0304 code as continued misfiring can damage the catalytic converter and cause further engine problems. If you must drive, keep speeds low and get the issue diagnosed immediately.

Q: How much does it cost to fix P0304 on a Subaru?

Repair costs vary widely depending on the cause. Spark plug replacement costs $100-200, ignition coil replacement costs $150-300, fuel injector cleaning costs $50-150, while internal engine problems can cost $1,500-4,000 or more.

Q: What causes cylinder 4 misfire in Subaru engines?

Common causes include faulty spark plugs, bad ignition coils, clogged fuel injectors, vacuum leaks, low compression due to worn rings or valves, and timing issues. Carbon buildup and fuel quality problems can also contribute to misfires.

Q: Will P0304 cause my Subaru to fail emissions testing?

Yes, P0304 will typically cause your vehicle to fail emissions testing as misfires increase harmful exhaust emissions. The code must be resolved and the readiness monitors must complete before passing emissions testing.

Q: How do I prevent P0304 from happening again?

Regular maintenance including timely spark plug replacement, using quality fuel, keeping up with oil changes, replacing air filters, and addressing check engine lights promptly can help prevent misfires. Avoid extended idling and use fuel system cleaners periodically.

Abstract

Subaru error code P0304 indicates a misfire detected in cylinder 4 of your engine. This means the fuel and air mixture in cylinder 4 is not burning properly, which can cause rough idling, reduced power, and potential engine damage if left untreated.