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・Fair and transparent pricing

Get a quote

What others are asking

Q: What precautions should I follow when using the Intelligent Key?

Your car’s Intelligent Key is a key, a receiver and a transmitter. It functions as a remote to lock and unlock your doors, but it also ties into the car’s immobilizer system. Without it, you can’t go very far. It...

Q: Door handles not working

These door handles are known to be weak and break over time. In order to replace your door handles the door panels will need to be removed to gain access to the mounting hardware. From that point the handles are...

Q: Why does my car cut off when I lift my foot off the gas?

If you had a diagnostic test done and they said nothing is wrong, then what did they say about the stalling? I would say to have a qualified mechanic like one from YourMechanic come to you and do a real...

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
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.