As far as the idle, check for vacuum leaks. Also, check the idle air control valve. If the check engine light is on, have the computer scanned. Most parts stores will do it for free.
The noise could be many things. A knock can be caused by a engine bearing, belt driven accessory. You need to locate a more specific area that it comes from.
Thursday, March 3rd, 2011 AT 1:13 PM