Skip the auto shop - Our mechanics make house calls

Q: Car misifires under load, P0300 code

asked by on

My car has been idling fine. However, when the car is under load, it starts misfiring. I had the code reading of the vehicle and the P0300 error code appeared. What do you think is the matter with my car?

A: Hello. The P0300 code refers to a detection...

Hello. The P0300 code refers to a detection of a misfire in one of the cylinders. If the car idles fine and only acts up during acceleration with this code coming up, then it is usually caused by a fuel system issue. A weak fuel pump will cause low pressure and this will occur. There are other sensors that can also cause this but the pump is the most common. I usually check the fuel pressure first. If you are planning on having this repaired, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose the misfiring issue more thoroughly and make any repairs that are needed.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Engine Misfire

The code #6 you mention is not a recognized code. The engine being hard to start may be from a bad starter, or bad battery. The fuel pressure may be low and the vibration could be caused by bad...

Q: Car vibrates while idling

The crankshaft damper has been known to cause an engine vibration, due to it separating and getting out of balance, causing the engine to vibrate. If this is the case, it may need to be replaced. I recommend having a...

Q: I think my Distributor O ring is leaking and can see oil run down from under the Distributor

On your '86 Cadillac Deville, you should be able to find the timing marks down toward the bottom of the water pump. There will be a cylinder looking tube attached to it with numbers on it reading from 0-20. These...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...