Can anyone give some ideas on why my accent would be running rough? I changed the spark plugs because they were all fouled out and it still runs rough. No code is showing, gas milage sucks. I recently put a new alternator in it, not sure if that has anything to do with it.

Its a 2012 hyundai accent hatchback.

  • The Alternator is not going to be the problem; find out why the spark plugs were fouled. Pull one of the new ones and see what it looks like. May be a dirty MAF or similar causing rich running, but there's not much information to go on yet.
    – PeteCon
    Commented Aug 2, 2016 at 15:31
  • How is the engine air filter? Maybe a bottle of fuel injector cleaner in the gas tank.
    – Old_Fossil
    Commented Aug 2, 2016 at 19:49
  • Check all your fluids too and make sure your oil and trans fluid look good and are at proper levels. I assume you gapped the spark plugs as per the spec, you used the correct OEM spark plug as per the spec (sometime the performance plugs can cause issues), consider changing your spark plug wires as well if you've not. Double and triple check that you used to corrected plugs as per the OEM spec and that you gapped those or checked the gaps if they were pre-gapped?
    – Facebook
    Commented Aug 5, 2016 at 18:46

1 Answer 1


There are multiple possibilities that could cause the issues you describe

A severely clogged air filter. If your air filter is clogged then you will be pulling less air into your engine and therefore increase your ratio of fuel and air that is being burned in your motor. This can lead to a very rich (too much fuel and not enough air) condition which would explain your fouled spark plugs.

If you have a check engine light on you may have an issue with your MAF (mass airflow sensor) or an oxygen sensor that COULD be leading to your rich condition which fouled your spark plugs initially.

There is also the possibility that your catalytic converter (a component of your exhaust system that burns unburned fuel) may be clogged from your fuel richness issue. This would further exacerbate your issue of a rough idle and foulded spark plugs.

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