A car with a cylinder 4 misfire may still run, but driving with an active misfire is not recommended. Rough running and poor acceleration can make the car’s response less predictable, and continued driving may lead to further engine damage. Limit further driving and arrange a diagnosis. If the car is running too poorly to operate predictably, stop somewhere safe and arrange professional assistance.
Can you drive with a cylinder 4 misfire?
Being able to keep the engine running is not the same as the car being safe or advisable to drive. A misfire can cause rough idling, poor acceleration and reduced fuel efficiency. Sluggish or uneven acceleration can be particularly concerning when merging into traffic or overtaking another vehicle.
OBDeleven’s P0304 guidance describes these drivability effects, while Edmunds advises against driving with P0304. There is no supported safe distance or time allowance for driving with this fault, so do not rely on a set number of miles or days. Avoid unnecessary journeys and arrange prompt diagnosis.
If the vehicle cannot be driven predictably, pull over in a safe place and seek professional help rather than continuing.
What problems can driving with a misfire cause?
As well as making the car harder to drive smoothly, continued driving with P0304 may lead to further engine damage, according to Edmunds. This is a potential consequence, not a guaranteed outcome. The available information does not establish how quickly damage could occur, identify a particular damage mechanism, or provide a period of driving that can be considered safe.
Reduced fuel efficiency is another possible effect. Poor or inconsistent acceleration can also leave the car less responsive when you need to increase speed. These are reasons to limit driving and have the fault investigated; they do not prove that any particular component has failed.
What does P0304 mean?
P0304 means the vehicle’s system has detected a misfire associated with cylinder 4. The standard code uses a zero: P0304, not “PO304” with the letter O.
The code identifies a detected condition and the cylinder involved, but it does not establish the underlying cause or prove which component needs replacement. Symptoms alone cannot confirm that cylinder 4 is misfiring. A diagnostic scan can show whether P0304 is stored, but further diagnosis is required to identify why it has appeared.
For broader background, see our guide to common causes of a cylinder misfire. That general information does not identify the fault in an individual car.
What does a cylinder misfire feel like?
Possible signs include rough idling, poor acceleration and reduced fuel efficiency. These symptoms can be associated with a misfire, but they do not prove that cylinder 4 is affected or explain why the car is behaving that way.
A scan and proper diagnostic assessment are needed to establish whether P0304 is present and to investigate the cause.
What should you do about a P0304 misfire?
Start by identifying the fault rather than replacing parts based on the code alone. A diagnostic scanner can retrieve stored trouble codes and, where available, freeze-frame data. Freeze-frame data is a snapshot of engine conditions at the point the fault was recorded and may include details such as engine load, temperature and RPM.
- Record all stored diagnostic codes and review any available freeze-frame information.
- If a code is cleared but immediately returns, treat the issue as ongoing and continue diagnosis rather than taking a test drive. Clearing a code is not a repair.
- If the cause is unclear, or the car is running poorly, arrange qualified diagnosis.
- Do not assume a particular part is responsible simply because P0304 has been stored.
The available information does not provide a confirmed cause, a vehicle-specific test procedure or repair instructions for your car. It therefore cannot support a guaranteed quick fix or a recommendation to replace a particular component. Repair difficulty depends on what diagnosis finds, so P0304 alone cannot show whether the repair will be straightforward.
There is also no reliable repair-cost figure to give without identifying the cause and considering the vehicle involved. Ask for an estimate once the fault has been diagnosed rather than relying on a generic price.
Can a misfire go away by itself?
The available information does not establish whether a misfire will resolve without repair. A warning light or code that temporarily disappears is not proof that the underlying issue has been fixed. If P0304 or the symptoms return, have the vehicle diagnosed. If a cleared code immediately comes back, treat it as an ongoing fault.
If your check-engine light is flashing, read our guide to what to do about a flashing check-engine light. Owners comparing cylinder-specific codes can also see our guidance for another cylinder-specific misfire code. If you own a Volkswagen Tiguan, see the separate P0304 guide for Volkswagen Tiguan owners; its vehicle-specific information should not be assumed to apply to other cars.