tyler_ ... 12/31/2012
1999 Mercury Cougar Base 4 Cyl 2.0L
rough idle, whistling noise
the alternator went on my cougar, so i replaced it. then the day after i replaced it it started acting up. it started idling rough . as long as you are going it runs smooth. so i replaced the plugs and wires, still same problem. and just recently it started making a whistling noise and stalling sometimes when coming to a stop.
sounds like vacuum leak, check for leak by spraying ether around vacuum hoses and connections with engine idling.engine speed will increase when ether finds the leak. would start in area around around alternator( being careful not to spray alternator) as you may have knocked o hose loose or disturbed e hard brittle hose and broken it. replace bad hoses or reconnect any that have been knocked loose.