Odd sound on cold start

[smartky]

Is anyone else getting on odd sound from the engine compartment upon a cold start? I don't know if mine has been doing it all along, or if I just noticed it recently. I have not noticed it on a hot or warm start, only cold. Basically, turn the key to activate the starter and release. Once the engine starts and a moment (not exactly sure how long that "moment," maybe a second or two) passes, you'll hear what sounds like an electric motor spinning up. It will stay "up" for about 10 seconds or so, and then it will spin down. Gear engagement makes no difference. Forward or reverse movement make no difference. HVAC fan in off position. Radio off. I can hear the fuel pump when I turn the ignition on, so I know what it sounds like and that's not it. I don't think it's the radiator fan as the sound seems to be coming from the rear (and the sound seems too "heavy" to be a fan). My best guess is that it's the starter motor, but that doesn't make sense since the sounds ramps up after the engine has started and the starter has disengaged (and there's no gear crash from a running-engine starter engagement). Never noticed it any time except for after a cold start. Any one else heard this or have any thoughts?

[bottlerocket]

Its normal

[Arch]

No worries. It's part of your emissions system (secondary air pump) and could last up to about 30 seconds, but typically goes away much quicker than that and most often isn't heard at all.

Arch

[SuperGeek]

I get the same thing, it's normal. Per my ScanGauge, immediately after the noise stops, the car goes into Closed Loop mode and is ready to drive. I just consider it a reminder to let the engine warm up before tearing off into traffic.

[SmartDigger]

Most likely a air fan charging the cat until the temp is up to operating temp.