No, you can't use your Irish passport to enter the Unites States by law if you are a U.S. citizen.
U.S. Code § 1185 (b)
Citizens
Except as otherwise provided by the President and subject to such limitations and exceptions as the President may authorize and prescribe, it shall be unlawful for any citizen of the United States to depart from or enter, or attempt to depart from or enter, the United States unless he bears a valid United States passport.
http://www.law.cornell.edu/uscode/8/1185… ..
http://travel.state.gov/travel/cis_pa_tw… ..
To travel on the Irish passport you would need to hold an online travel authorization (ESTA) from the US CBP.
http://www.cbp.gov/xp/cgov/travel/id_vis… ..
You better get an emergency passport issued by the U.S. Embassy before you travel.
http://dublin.usembassy.gov/service/pass… ..