sell sy a bill of goods

For poor advice, bum steer might be better, the other involves swindling:
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bum steer

False or misleading information; poor advice. For example, Gene felt
his doctor had given him a bum steer, as he hadn't lost any weight on
the diet. [Slang; c. 1920]

http://www.answers.com/topic/bum-steer
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sell a bill of goods

Deceive, swindle, take unfair advantage of, as in He was just selling
you a bill of goods when he said he worked as a secret agent, or Watch
out if anyone says he wants to trade bikes with you; he's apt to be
selling you a bill of goods. The bill of goods here means "a dishonest
offer." [c. 1920]

http://www.answers.com/topic/sell-a-bill-of-goods
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You should also see:
bum steer
http://www.wordwizard.com/ch_forum/topic.asp?TOPIC_ID=6169