Skip the auto shop - Our mechanics make house calls

Q: P0300 codes while idling

asked by on

I have been getting p0300 codes on my van this past week. The codes only appear while idling. I’ve checked and repaired a few vacuum lines, cleaned the mass air flow sensor, cleaned the throttle body, installed new plugs, cap and rotor, ran fuel injector cleaner through the fuel system, checked the for intake manifold leaks and more. So I decided to pull the plug on the mass air flow sensor and all of my misfires were gone. My van ran great with no problems! I bought a new mass air flow sensor and installed it. I cleared the mass air flow code and started it up. Less than a minute later p0300 codes showed up again. So I unplugged the new one and the misfires were gone. Can you tell me what’s going on? Should I return my new MAF sensor? Is this something I should worry about?

A: Hello. If unplugging the MAF sensor causes ...

Hello. If unplugging the MAF sensor causes the engine to run better then there is a secondary air leak into the engine. This means that there is a vacuum leak from someplace. Most of the time on this engine it is from the intake manifold. It may also be a rich condition that can be from the fuel injection unit.

I usually check this by installing a scan tool to see what the fuel trim readings are. This will tell me if it is getting too much air or fuel and where to start. I have seen more intake manifold gasket failures on this engine than anything else. If you are going to have this repaired, consider YourMechanic, as a certified mechanic can come to you home or office to diagnose your Check Engine Light and repair it accordingly.

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・Fair and transparent pricing

Get a quote

What others are asking

Q: Trying to replace the alternator but we can't get the air compressor enough out of the way.... Any advice would be appreciated

Hello, thanks for writing in about your Jeep Compass. You have to lower the compressor and pull it towards the outside as far as possible. Then move A/C line to other side of the alternator battery stud. It is a...

Q: Overheating

When you put pressure in the radiator you are only going up to about 15 psi, but when a cylinder fires, it puts out a lot more than the compression test showed at 125 psi. This is why you are...

Q: Misfire in cylinder 6. GMC Sierra 1500.

Hey there. You need to have the engine compression tested to see if you have a leaking valve or rings. You could try to have the combustion chamber cleaned of carbon and see if the problem improves. This may be...

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 Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...