Error code 2121

[MMGreger@aol.com]

I've been having problems with my 91 100 lately.   It wants to stall after 
being driven 1 to 1 1/2 miles after a cold start.   At that point it drops 
back to idle for 30 secs or so, at which point it begins to run normally 
again and will not restall until after another cold start.   I pulled the 
fault codes and got a 2121 which translates into "Idle Switch".  My questions 
are;   1. has anyone else had a similar problem, 2. can the idle switch be 
responsible, and 3.  where is the idle switch located and how do I identify 
it?   I have a parts car which was operating normally before an accident, so 
I can easily change out parts.  Thanks.