P0300 Code, Symptoms, Causes, How to Fix

P0300 Code, Symptoms, Causes, How to Fix

P0300 means that two or more cylinders are misfiring. A misfire happens when fuel is not getting burned in a cylinder. A misfire from two or more cylinders can be caused by many reasons including, bad spark plugs, timing issues, faulty ignition system, fuel pressure issue, faulty catalytic converter, and even internal engine failure.

Contents

What Does the P0300 Code Mean?

The P0300 code indicates that there are random or multiple misfires between pistons.

Is the P0300 code bad?

The short answer is yes. Until you find what is causing the misfire, you could cause more serious sometimes irreversible damage to your car’s engine.

Can you drive with the P0300 code?

If you don’t know what is causing your misfire it is hard to give a solid yes or no answer. Generally, the answer is no, due to the effects that can become of an undiagnosed misfire. You can drive it to a secure place like a shop or your home. But, I would advise not driving daily until you or someone you trust can tell you what’s wrong.

Can an 02 sensor cause a P0300 code?

Yes, sensors can play a part in the P0300 code. The 02 sensors as well. Located within the exhaust system your vehicle will usually have two or sometimes more 02 sensors.

When the 02 sensor goes bad, the engine can run rich, which can cause a cylinder not to fire all the time.

Alternatively, if your engine runs lean, the air to fuel mixture is too light. So, when your plug fires there isn’t enough to have a conduct a complete cylinder fire.

Symptoms

  • Check engine light is on or flashing
  • Engine runs rough
  • Lack of power
  • Fuel smell from engine exhaust
  • Hesitation or jerking during acceleration

Causes

  • Faulty or worn spark plugs
  • Faulty spark plug wires or coils
  • Distributor failure
  • Bad head gasket
  • Internal engine failure

Repair

  • Replace spark plugs
  • Replace ignition coils
  • Replace fuel injectors
  • More advanced internal engine repair
  • Engine replacement

Diagnosis 

The good news for the P0300 code is typically the culprit is the spark. This means that the spark plugs, spark plug wires, or ignition coils are at fault.

  • Test spark plugs and ignition coils
  • Test fuel injectors

The best way is to test at the connector by conducting an ohm reading across the injector. A high ohm reading indicates that there is a failure within the injector.

  • Exhaust gas leak test

(At the auto parts store, you can buy an exhaust gas leak tester. What this test does is changes the color of the dye in the test tube, if it detects exhaust gases in the cooling system. This test allows you to conclude whether or not there is a leak in the head gasket. The instructions are included and are user-friendly!)

  • Compression test

Testing this is simple with a compression tester. This tool can be used without taking the cylinder head off. The tool is threaded into the spark plug hole and has a gauge. This way, when you crank the engine you can see what the compression value is. Refer to your OEM manual to find the spec for your specific vehicle.