I would put money on a hard failure of the idle control valve being caused by burnout due to a gummed up mechanism. I.e. regular service could extend service life indefinitely. However, if you are getting the same symptoms after a few months, either you didn't adequately clean it or the fault is elsewhere.
Steve
__________________
'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7
|