P0300 Random misfire on more than one cylinder

Check this first

If the check engine light is flashing, stop driving – raw fuel is going into the catalytic converter.

What usually fixes it

In the order a good shop checks them. Typical total: $140–$925 at $130 an hour.

1. Spark plugs

   $196–$404

   Worn plugs misfire under load first; they're the usual cause past 60,000 miles.

2. Ignition coils

   $165–$595

   A weak coil drops out when it gets hot.

3. Vacuum leak

   $171–$444

   A big leak upsets several cylinders at once.

4. Fuel delivery

   $268–$925

   Low pressure or dirty injectors starve every cylinder a little.

Code titles are the generic SAE definitions. Prices are typical US parts and labor for a common car or light truck – a guide for judging a quote, not a quote. Always confirm a repair against the vehicle in front of you.