I have a 1990 Honda Accord EX 5 Spd. When I drive my car it seems like I am losing power. I have to press on the gas peddle to make it really move. But after my check engine light comes on it runs almost perfectly. I can still feel very little hesitation but not as bad as when the check engine light was off. It sometimes comes on immediately and sometimes it takes a while. Usually no longer than 5 minutes or so. I asked a mechanic about it and he said that it was more than likely the oxygen sensor and when the check engine light comes on it is bypassing the sensor. Is this true? Please help. Any ideas?