2002 honda accord flashing check engine light and extremely rough idling?

i added some oil because i was low, that didnt seem to fix the problem. When the car is idling its is a very slow pop-pop-pop-pop but when i give it gas it goes away. Also, if im driving on flat or slighly downhill ground the light stays on, but stops blinking. When i go uphill it begins blinking again. Any ideas?

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