P0300 Code Comes and Goes! Troubleshooting Guide to Fix The Persistent Misfires!

When the P0300 code comes and goes, it’s called intermittent misfiring. A faulty spark plug or ignition coil usually causes this problem. Moreover, clogged fuel injectors, vacuum leaks, a clogged catalytic converter, or a defective crankshaft position sensor can also contribute to this.

The following sections will discuss why the P0300 code comes and goes.

P0300 Code Comes and Goes

What Does Code P0300 Mean?

The P0300 code is a generic diagnostic trouble code that indicates a random misfire in one or more cylinders. When this code appears, the engine control module (ECM) has detected that the engine is not firing correctly, and it cannot pinpoint the exact cylinder causing the problem.

Sometimes, a P0300 code may be accompanied by other codes indicating which cylinder or cylinders are misfiring. However, if the ECM cannot identify a specific cylinder, it will set the P0300 code instead.

Why Does The P0300 Code Come and Go?

If the code P0300 comes and goes, the misfire occurs under specific driving conditions. This phenomenon is called “intermittent misfiring.”

An intermittent misfire occurs only occasionally and is not consistent enough to trigger the P0300 code every time. This can make diagnosing and repairing challenging, as the problem may not be present when the vehicle is brought in for service.

Is It OK To Drive With A P0300 Code That Comes and Goes?

No, driving with a P0300 code that comes and goes is not recommended. Even if the code disappears for a while, the underlying issue causing the misfire remains. It could be causing damage to the engine over time.

An intermittent misfire can cause unburned fuel to enter the exhaust system, damaging the catalytic converter and other components. It can also cause increased wear and tear on the engine and decrease fuel efficiency and performance.

Additionally, if the misfire is severe enough, it can cause the engine to run poorly or stall, which could be dangerous if it happens while driving.

How To Fix P0300 Code That Comes and Goes?

When a P0300 code comes and goes, it can be challenging to diagnose and repair. However, it is essential to address the issue as soon as possible, as a misfire can cause damage to the engine over time. 

What could cause a P0300 code that comes and goes?

Here are the reasons:

  • Faulty spark plugs or ignition coils, 
  • Clogged fuel injectors, 
  • Low fuel pressure, 
  • Vacuum leaks, 
  • The clogged catalytic converter, or 
  • Faulty crankshaft position sensor

Symptoms of P0300 Code 

  • Check engine light may come on and go off intermittently
  • Rough or uneven idle
  • Engine hesitation or stumbling
  • Poor acceleration
  • Decreased fuel efficiency

Solution One: Replace the Faulty Spark Plug or Ignition Coil

Worn or faulty spark plugs or ignition coils can cause misfires, so replacing these components can often fix the issue.

It would be best if you first allow the engine to cool down to ensure the spark plugs are in good condition. Then, locate the spark plugs and remove them using a spark plug socket and ratchet. If you find the stuck plug is stubborn to remove or stuck you can follow this guideline.

Inspect them for wear or damage, check the gap using a spark plug gap gauge, replace them if necessary with the correct type of spark plug, and finally, reinstall them to the torque specifications listed in your vehicle’s service manual.

Persistence of the P0300 code after changing spark plugs could mean a faulty ignition coil. To check the ignition coil, locate it using the vehicle’s manual. Inspect it for signs of damage and use a multimeter to test its resistance. If the reading is outside the acceptable range, replace the coil. 

You can also perform a spark test to see if the coil produces enough voltage. If the spark is weak or absent, replace the ignition coil.

Additionally, you can swap the suspected faulty ignition coil with another one of the same types to see if the problem moves to the other cylinder.

Solution Two: Clean or Replace Fuel Injectors

Cleaning or replacing clogged fuel injectors can often resolve the issue. If the injectors are only slightly clogged, a fuel injector cleaning service may be all that is needed. This involves using a special cleaning solution run through the fuel injectors to remove any debris or deposits that may obstruct their performance. 

If the fuel injectors are severely damaged, they may need to be replaced. This involves removing the old fuel injectors and installing new ones designed to fit the specific make and model of the vehicle.

Solution Three: Faulty Fuel Pump or Fuel Pressure Regulator

The fuel pressure regulator and pump work together to maintain consistent fuel pressure at the fuel injectors. If either of these components fails, it can result in low fuel pressure, which can cause misfires.

You will need a fuel pressure gauge compatible with your vehicle’s fuel system to check the fuel pressure. Follow the instructions in your vehicle’s service manual to properly connect the gauge to the fuel system.

Start the engine and allow it to be idle while monitoring the fuel pressure gauge. The fuel pressure should be within the specifications listed in your vehicle’s service manual. If the fuel pressure is too low, it could be due to a faulty fuel pressure regulator or fuel pump.

To check the fuel pressure regulator, remove it from the fuel rail and inspect it for signs of damage or wear. You can also use a vacuum pump to test the regulator by applying a vacuum and monitoring the fuel pressure gauge. If the fuel pressure does not increase with the vacuum applied, the fuel pressure regulator may be faulty and should be replaced.

To check the fuel pump, you will need to access it, which may require removing the fuel tank or accessing it from underneath the vehicle. Once you have access to the fuel pump, you can use a multimeter to test the electrical connections to the pump. If there is no power or a weak power signal to the fuel pump, it may be faulty and should be replaced.

Replacing a fuel pump is a lengthy and complex process; thus, it should be done by a professional. You should take the vehicle to a mechanic if you have a faulty pump. 

Solution Four: Repair Any Vaccum Leaks

Vacuum leaks can occur when there is a crack or hole in any of the components of the intake system, such as the intake manifold gasket, vacuum hoses, or throttle body gasket. 

An engine vacuum gauge can be used to measure the vacuum pressure in the intake system to check for leaks. If the pressure reading is lower than usual, it could indicate a vacuum leak.

Once a vacuum leak is identified, it is crucial to repair it immediately. The exact repair method will depend on the location and severity of the leak. A simple fix like tightening a loose hose clamp or replacing a cracked hose may be all that is needed. However, in other cases, more extensive repairs, such as replacing the intake manifold gasket, may be necessary.

Solution Five: Clean the Catalytic Converter

The catalytic converter can often get clogged, which may cause intermittent misfiring. This occurs when the blocked or damaged converter restricts exhaust gas flow, causing pressure buildup in the exhaust system. This buildup can cause backpressure, affecting the engine’s combustion process and leading to misfires.

The back pressure may only occur under certain driving conditions. For example, misfires may only happen when the engine is under a heavy load or when driving uphill. Sometimes, the misfires may only occur at certain speeds or RPM ranges. This explains the appearance of the P0300 code at high speeds.

In such cases, inspect and clean your catalytic converter.

Solution Six: Replacing the Crankshaft Position Sensor

The ECM uses the crankshaft positioning sensor to detect misfires. So, if the crankshaft position sensor is not working, the P0300 may come and go.

But first, you need to make sure that it’s working. To test a crankshaft position sensor, locate it near the crankshaft pulley or flywheel. Then disconnect the electrical connector and measure its resistance using a multimeter. The value should be within the 200-1000 range; check your owner’s manual for confirmation.

If the sensor is faulty, replace it with a new one.


When the P0300 code comes and goes, it’s tough to pinpoint the actual problem. That’s why it’s better to get advice from professionals if you get confused.

You should only let the situation prolong or drive with solving the code first, as it may damage your engine even further and cause costly repairs. 

Last Updated on April 28, 2024 by Rifen

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top