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

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: RPM's fluctuate while idling and sometimes it dies. Getting codes for multiple misfires and knock sensor.

Hi there. Check the fuel injectors and see if they are working or not. While the engine is running, unplug one injector harness at a time. If the engine begins to hesitate, then the injector was working. If the engine...

Q: car rides too low in rear, shocks have lost air

The rear shocks also support the rear of the car and regular shocks would not support the vehicle for you. There may be an aftermarket air shock replacement that is cheaper than the dealer part, but for the most part...

Q: Car shakes when accelerating from 1st gear - 2001 Nissan Pathfinder

Hello. If your vehicle is shaking when accelerating from first gear, and not shifting into overdrive or the higher gears, then there is likely some sort of issue with the transmission. A few things that can cause these symptoms are...

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 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...
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...