171,174 can be caused by vacuum leaks, pcv valve, mass air flow failure or low fuel pressure. Mass air flow cleaners have little or no effect. Assuming you cleared the codes, they will return after failing 3 drive cycles if there is still an issue. You need to monitor the long term fuel trims to diag the failure.
As far as idling, it could be a vacuum leak, throttle body or idle air control.
Roy
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Saturday, September 21st, 2013 AT 2:11 AM