When I start my '94 Z28, a electric whirring noise starts up for about 2-3 minutes then shuts off. Someone told me it was the air pump. What is the air pump do and what can I do about this noise? Thanks guys.......Pete

 

Yup, just the air pump, supposedly they pump hot air into the catalitic converter allowing for better air flow when the engine is still cold. However, Ive removed mine and have yet to have a problem (when I had a cat)

 

OK, did yours make the whirring noise before you took it off?

 

Yup, if you dont want to remove it right away, but want to get rid of the noise, just unplug it (dont remove the relay-throws SES light, just unplug the wiring from the airpump)