Whining/whirring sound

[#1weatherman]

I have a '92 LT1 coupe, and around 45-60 seconds after start up I hear a whining/whirring sounds that lasts maybe 3-5 seconds. the sound resembles that of an electric motor pushing something up or down, and it is not the radio antenna, because it happens whether or not the radio is on, plus the sounds is coming from under the hood. can anyone shed some light on that please? thanks. Jim aka #1weatherman

[96GS#007]

Originally Posted by #1weatherman

I have a '92 LT1 coupe, and around 45-60 seconds after start up I hear a whining/whirring sounds that lasts maybe 3-5 seconds. the sound resembles that of an electric motor pushing something up or down, and it is not the radio antenna, because it happens whether or not the radio is on, plus the sounds is coming from under the hood. can anyone shed some light on that please? thanks.

Jim aka #1weatherman

Air Injection Reaction (AIR) Pump, part of the secondary system for emissions. The sound is Perfectly normal. It should run at start-up until the car goes into closed loop or ~90-120 seconds. There's a lot of other stuff going on at cold start (ie slightly higher idle speed) that can mask the sound initially. Specifics of operation are in the Factory Service Manual.

[#1weatherman]

Thanks 96GS#007 for the reply. I figured it was nothing to worry about. the sound I mentioned must be the pump shutting off, based on the timing you provided.

Jim aka #1 weatherman

[ssdan]

good question as I have been wondering the same thing.

[motor city dave]

Originally Posted by ssdan

good question as I have been wondering the same thing.

Same here.....Thanks.

[ssdan]

just got mine, so I haven't got a shop manual yet. It also seems as if my exhaust is quieter for a period after cold start as well, is that related?