The car is coding an engine misfire P0300 and P0303 and is physically chugging, has no power in 1st gear and literally feels like the car is going to shut down while in idle (chugs violently and the dash lights flicker, etc.). All the spark plugs and ignition coils are now new but this has not changed the misfiring or coding issues.
What would be the next step for an amateur DIY'er?
My car has 300000 miles.
My car has an automatic transmission.
Code P0300 relates to a random cylinder misfiring which can be caused by many different issues such as the following:
I would recommend starting by checking for intake leaks as these are a common cause for this as well. Code P0303 relates specifically to cylinder #3 and can be caused by the same issues as mentioned above. This code may also be related to code P0300 as well.
If you would like to further assistance with this, a certified technician from YourMechanic can come to your location to diagnose the misfire firsthand so that the proper repair can be made.
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