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

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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.

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.

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