P0300: Random or Multiple Cylinder Misfire Detected
P0300 means the engine computer detected misfires that were not isolated to one cylinder. It is logged when the crankshaft speed fluctuates in a pattern consistent with cylinders failing to fire, either randomly or across several cylinders at once.
Can I still drive with P0300?
No, if the light is flashing
A flashing check engine light means an active misfire dumping raw fuel into the exhaust, which can destroy the catalytic converter within minutes of driving. Pull over and arrange a tow. If the light is steady and the engine runs smoothly, drive straight to a shop and no further.
What you will actually notice
- Engine shakes or stumbles, especially at idle
- Loss of power and hesitation on acceleration
- Check engine light, often flashing
- Rough running that may smooth out at higher speeds
- Smell of unburnt fuel from the exhaust
Causes, ordered by how often they turn out to be the fault
1.Worn spark plugs or ignition coils
Very commonThe first place to look, particularly if plugs are past their service interval.
2.Vacuum leak
CommonOften shows lean codes alongside the misfire.
3.Failing fuel injectors or low fuel pressure
CommonStarves several cylinders at once.
4.Worn ignition wires or a failing distributor on older engines
CommonApplies to engines that still use them.
5.Carbon build-up on intake valves
Less commonA known issue on many direct-injection engines.
6.Timing chain stretch or incorrect valve timing
Less commonUsually accompanied by correlation codes such as P0016.
7.Low compression from mechanical wear
RareThe expensive outcome. Confirm with a compression test before assuming it.
How to diagnose it, cheapest test first
Work down this list in order. The most expensive mistake with this code is replacing a costly part before ruling out a cheap one.
- 1
Read all codes, including any cylinder-specific ones
Free at most parts storesP0300 plus P0302 narrows the search to cylinder 2 immediately.
- 2
Inspect spark plugs
LowTheir condition tells you a great deal: oil fouling, coolant, or simple wear.
- 3
Swap an ignition coil to a different cylinder and re-test
Free if plugs are already outIf the misfire follows the coil, you have found it without spending anything.
- 4
Check for vacuum leaks
Free to inspectEspecially if lean codes are also present.
- 5
Test fuel pressure
ModerateRules out a starving fuel system.
- 6
Perform a compression or leak-down test
Moderate to highLast, because it is the most involved and points to the most expensive repairs.
What the repairs typically cost
| Repair | Estimated range |
|---|---|
| Spark plug replacementCost climbs sharply on engines where plugs are hard to reach. | $80 – $350 |
| Ignition coil replacementPer coil, including labour. | $120 – $500 |
| Fuel injector cleaning or replacementCleaning first, replacement only if it does not hold. | $150 – $900 |
| Intake valve carbon cleaningWalnut blasting on direct-injection engines. | $400 – $1,000 |
Estimate only. Ranges vary widely by region, vehicle and shop rate, and are not quotes. Always get a written estimate before authorising work.
Notes for specific makes
Volkswagen / Audi
Ignition coil failure is a well-known pattern on TSI and TFSI engines. Coils are often replaced as a set.
Ford
On some modular engines, a misfire that has been ignored can lead to a spark plug ejecting from the head. Do not delay.
BMW
Coils and plugs are the usual answer, but check the crankcase ventilation valve as well.
Honda
On VTEC engines, check the VTEC solenoid and oil level if plugs and coils test fine.
Common questions
My check engine light is flashing. What does that mean?
A flashing light signals an active misfire severe enough to damage the catalytic converter. Stop driving and get the car towed rather than driving it to a shop.
Why does it say random instead of naming a cylinder?
P0300 is set when the misfire moves between cylinders or affects several at once. That points at something shared — fuel, air or timing — rather than one bad coil.
Can bad fuel cause P0300?
Yes. Contaminated or water-affected fuel is a genuine cause, and worth considering if the problem began right after filling up.
How much does this cost to fix?
It ranges from a set of spark plugs to internal engine work, which is exactly why the diagnostic order matters. Rule out the cheap causes before anyone quotes you for the expensive ones.
Not sure which of these applies to your car?
Describe what the car is actually doing and get a diagnosis narrowed to your vehicle, or find a shop near you.
AI-generated and informational only. This is not a diagnosis of your specific vehicle and does not replace inspection by a qualified technician.