Answer by taking a quote from the following article:

James Buchanan Jr. was born in a log cabin in Cove Gap, Pennsylvania (now Buchanan's Birthplace State Park), in Franklin County, on April 23, 1791, to James Buchanan, Sr. (1761-1821), a businessman, merchant, and farmer, and Elizabeth Speer, an educated woman (1767-1833). His parents were both of Ulster Scottish descent, the father having emigrated from Milford, County Donegal, Ireland, in 1783. One of eleven siblings, Buchanan was the oldest child in the family to survive infancy.

In March 1860, the House created the Covode Committee to investigate the administration for evidence of offenses, some impeachable, such as bribery and extortion of representatives in exchange for their votes. The committee, with three Republicans and two Democrats, was accused by Buchanan's supporters of being nakedly partisan; they also charged its chairman, Republican Rep. John Covode, with acting on a personal grudge (since the president had vetoed a bill that was fashioned as a land grant for new agricultural colleges, but was designed to benefit Covode's railroad company). However, the Democratic committee members, as well as Democratic witnesses, were equally enthusiastic in their pursuit of Buchanan, and as pointed in their condemnations, as the Republicans.  The committee was unable to establish grounds for impeaching Buchanan; however, the majority report issued on June 17 exposed corruption and abuse of power among members of his cabinet, as well as allegations (if not impeachable evidence) from the Republican members of the Committee, that Buchanan had attempted to bribe members of Congress in connection with the Lecompton constitution. (The Democratic report, issued separately the same day, pointed out that evidence was scarce, but did not refute the allegations; one of the Democratic members, Rep. James Robinson, stated publicly that he agreed with the Republican report even though he did not sign it.)  Buchanan claimed to have "passed triumphantly through this ordeal" with complete vindication. Nonetheless, Republican operatives distributed thousands of copies of the Covode Committee report throughout the nation as campaign material in that year's presidential election.

what did they find?
corruption and abuse of power among members of his cabinet, as well as allegations (if not impeachable evidence) from the Republican members of the Committee, that Buchanan