Cylinder 4 Misfire Detected
The engine controller detected misfires in cylinder 4. A misfire code does not prove an ignition coil has failed: ignition, fuel injection, air leakage and mechanical compression problems can produce similar symptoms. Cylinder numbering depends on the engine. A flashing warning or severe shaking calls for stopping safely rather than continuing with an active misfire.
Can I keep driving?
A code alone cannot establish that driving is safe. With a flashing warning, shaking, overheating, unusual mechanical noise, smoke or substantial power loss, stop safely and arrange assistance. Otherwise ask a repair shop for vehicle-specific advice before driving further.
Flashing light, burning smell or smoke? Pull over safely. Danger to life: call 911.
What does this code mean for your car?
The same code can need different checks depending on the model and engine. Enter your vehicle details to find relevant sources and checks.
Symptoms
- Rough idle / shaking
- Stumbling and loss of power
- Check engine light, sometimes flashing
- Raw fuel smell from exhaust
Possible causes
- 1Worn or faulty spark plug
- 2Faulty ignition coil
- 3Clogged or faulty fuel injector
- 4Vacuum / intake air leak
- 5Low compression (valves, rings, head gasket)
These possibilities are not ranked by frequency and do not diagnose your vehicle.
Checks you can safely do yourself
Safe checks only: engine off and cold, car on level ground.
- With the engine off and cool, record companion codes, observed symptoms and service history. Do not disassemble components or clear codes before a shop saves the diagnostic evidence.
- Visually check the coil connector is seated and intact
- Check service records for when plugs were last replaced
When you need a shop
With shaking, power loss or a flashing warning, arrange assistance without continuing to drive. The shop should confirm cylinder identification and evaluate misfire data, ignition, injection and compression as appropriate.
How much does it cost?
A US repair estimate needs a diagnosis and a local shop quote.
No verified US repair estimate is available. Ask a local shop to diagnose the vehicle before quoting parts and labor.
Get 2-3 quotes
Investigate this code for my carFAQ
Can I keep driving with P0304?
A code alone cannot establish that driving is safe. With a flashing warning, shaking, overheating, unusual mechanical noise, smoke or substantial power loss, stop safely and arrange assistance. Otherwise ask a repair shop for vehicle-specific advice before driving further.
What can cause P0304?
Possibilities to investigate include Worn or faulty spark plug; Faulty ignition coil. The code does not prove a particular part has failed; diagnose before replacing parts.
If I clear the code, is it fixed?
No. Clearing a code does not repair its cause and may erase diagnostic evidence or reset readiness monitors. It may return when the monitor runs again. An unlit warning does not prove the vehicle is fault-free.
I saw this code on a car I'm thinking of buying - now what?
Don't run, don't shrug it off. Ask the seller for a shop diagnosis before you sign, and use what it finds to negotiate.
How much does fixing P0304 cost?
We do not have a verified US repair quote for your vehicle. Diagnosis, local labor rates and the confirmed repair determine the price. Get 2-3 quotes.