rough idle in cool humid weather

[Trevor Irwin]

My 1990 100 (non turbo)often exhibits a rough idle in (usually cool) humid
weather. tyically this happens when it is raining. i can usually keep the
engine running by pressing on the gas pedal, but sometimes the engine dies and
then won't start again for awhile, but after some time it starts up again
drives normally.

I looked through the archives and there was a thread from back in 1992
regarding similar problems--you can look at it here if you like:
http://www.audifans.com/archives/1992/08/msg00023.html
The suggestion there (which I had already suspected somewhat) was that the
problem lies in the computer that controls the fuel and air flow.

So what I am wondering is how can I verify that this is indeed the
problem, and, in anycase, how do I fix it. Thanks.

Trevor