My check engine light came on which produced a P0302 error code. I swapped out the engine coils in cylinder 2 & 4. I cleared the codes and started the car and ran it for a little bit. Now it is throwing P0304. So this tells me the engine coil is bad and should be replaced. If I have to replace one (I have 110,000 miles on the car), should I go ahead and replace all of them or will I be safe just replacing the 1? Also, what about spark plugs in these cars? Should they be replaced or are they good for the lifetime of the car?
Hello there, thanks for your question. I’d be happy to help. It does sound like a bad ignition coil is the cause of this P0302 trouble code. This is not uncommon since your car has over 100,000 miles. If it is just one coil causing the issue, then you should simply replace that one coil. Over time, the other coils will fail but that can be over a period of weeks, months, or even years. In my personal opinion, it is not worth changing them all if they are not bad. As for the spark plugs, they should be replaced at 100,000 miles. By not replacing them, the coils will work even harder which will cause them to fail prematurely.
If you would like help inspecting this or replacing the ignition coil, consider having an expert automotive technician from YourMechanic come to your home or office to make the necessary repairs for you.
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