Skip the auto shop - Our mechanics make house calls

Q: when my car idles it starts to miss and check light comes on po300 i replaced plugs and ignition coils still does it only at idle

asked by on

my car misses at idle only po300 top speed is good no misses replaced plug and ignition coils still misses at idle

My car has 173 miles.
My car has a manual transmission.

A: Hello. There could be a few different possi...

Hello. There could be a few different possible problems that would need to be checked. The complete intake air system has to be checked for vacuum leaks or cracked intake air tube between the throttle body and airflow sensor. Check the airflow sensor for contamination. Have the engine checked for acceptable cylinder compression of between 142 psi and 185 psi with less than 14 psi difference between cylinders. The O2 sensors should be working normal at idle switching between 5 to 10 times a second. Contact a technician, like one from YourMechanic, to inspect the misfire on your vehicle and replace any failing parts.

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

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: Air conditioner making noise

You have an A/C leak. Dye needs to be added to the system, and the system needs to be recharged. Pressure gauges need to be attached to verify proper A/C system operation. You may also have a compressor issue that...

Q: DRL won't turn off

Hello there, a few different faults can cause the daytime running lights to stay on. The most likely would be the headlight switch, DRL relay, or a wiring issue. Have a certified technician, such as one from YourMechanic, diagnose your...

Q: How do I remove the fuel cap?

You need to remove the fuel cap in order to refuel your vehicle. To do so, simply rotate the fuel cap counterclockwise until it releases, then place it on the cap holder located on the inside of the fuel-filler door....

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...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.
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.