I have a 4.7L V8 that experiences irratic, fluctuating idle speeds when idling. When first started the engine can spend several seconds at approximately 2,000 rpms, then it may decrease to 1,500, 1,200 or even down to 700, then it tends to cycle up and down varing by several hundred rpms, most frequently in the range of 700-1,000.
You can even note this rpm "cycling" when in gear at a full stop. It is not noticeable at driving speeds, of course, nor does it happen all the time, however it is doing it most of the time, almost consistently when the engine is cold.
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Thursday, May 7th, 2009 AT 1:04 PM