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?

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: Car uses quart of oil every 2 days

Hello. If you are losing oil that fast it is because you have worn out piston rings or valve stem seals. Adding a little oil to the cylinder during the compression test will help you narrow this down. If the...

Q: While fogging my 7.4L (Carb) boat engine, the plastic straw shot into the cylinder. Will it simply burn away?

Hello and thanks for your question. Remove the exhaust manifold to the side that has the straw. Turn the engine over by hand to open the exhaust valve. Use your flexible grabbing tool to reach in the cylinder and take...

Q: rpm drops to idle at highway speeds, pull over and restart.

Hello. There is simply no way of knowing without being able to perform some tests, and ask some further questions. When this happens, do any warning lights come on? Even if they don't, have the vehicle scanned for diagnostic troubleshooting...

Related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
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...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.