Q: P0300 Random misfire.

asked by on

Having random misfire issues. P0300 code. I replaced all coils and plugs. It seemed to fix it for about a month, then it started misfiring again. So I replaced the MAP sensor, and the mass airflow sensor. That didnt fix it either. I can go a few days with no issues, then out of nowhere it misfires again and throws a P0300 code. I already paid Chevy 125 buck for them to tell me it just needed new plugs and coils. Any other small fixes I can try myself before I have to pay them again to probably be wrong?

My car has 104000 miles.
My car has an automatic transmission.

Without seeing the fuel trim readings in the computer to see if the engine is running too lean then it would be a guess that you have a vacuum leak between the mass air sensor and the intake manifold or one of the connections to the manifold. Have engine checked for any vacuum leaks. Replace the PCV valve and make sure there is no vacuum leaks.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 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
  1. Home
  2. Questions
  3. P0300 Random misfire.

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: When I accelerate, my car hesitates, the rpms bounce, and sometimes i have a missfire flashing CEL

Hello and thank you for your question. With having your engine with bank 1 being lean (lack of fuel), the symptoms are showing that there is a problem with fuel delivery or excessive heat. If the EGR valve was to...

Q: Part fell from above brake/gas pedals.

The part is not a Chevrolet part but an aftermarket alarm system that was installed on the truck. Most of the time the part is just stuffed up inside the dash or wire tied to anything underneath the dash to...

Q: Stabilitrac & control light come on vehicle lose power to the enginc

Hi There, The stabilitrac is the truck's traction control system. It sounds like there is an error or fault in the traction control module causing this warning to come on. This can happen for a couple of different reasons. The...

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...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...