Loud air intake engine noise on startup

You just hear it better if you lower the roof or open your windows. It could just be your air intake. Unless your rpm`s are really racing to above 2500 or it is at high idle for a long time, you shouldn't kick it down. When it is cold your choke is helping to warm it up quickly. Nothing is really working properly until it reaches normal operating temperature. Let it warm up. If you are still concerned, listen under the hood for better perspective and when in doubt, take it to a professional.

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Take out the cabin air filter that is in the plenum behind the glove box. This will lessen the noise but you should get the unit serviced soon.

This is normal. All vehicles idle high at start up to get the engine to operating temperature. This is known as open loop. The computer ignores signals from O2 sensors to keep your engine running safely. Once it has warmed up, it will enter closed loop, and you will see a decrease in idle.

There is no way to estimate cost until you know the exact case of the noise. See the dealer for a test drive so a tech can listen to it.

2008 GMC Envoy is only equipped with one of two engines:
4.2L (254") 6-Cylinder SFI
5.3L (325") V-8 SFI

Niether of these engines are equipped with an EGR valve, so I guess the probability of that being the cause of your noise is pretty much zero to none.

If you believe the noise is being caused by the exhaust ststem, then the only way to verify that is to inspect the exhaust system. Leaks are easier to verify with the engine running.

With that said, there is also a Technical Service Bulletin (TSB) that is published by GM that addresses customer complaints about loud noise that is being caused by the electro-viscous engine cooling fan clutch. Some people describe it as exhaust noise and others describe it as the engine "racing" or "roaring".(even though the tachometer (if equipped) will be reading normal)

It basicly says that it can make noise on startup due to high rpm of the fan which goes away once the electric solenoids open and allow the fan to start free-wheeling. GM says this is normal operation. You might want to check to be sure this is not what you are hearing. (it can be pretty loud)

Boy, it sure seems a lot of work to capitalize every word...

It is an odd answer, but I think one or more of your intake valve are not sealing. Engines make a horrific amount of noise if you pull one spark plug, then start it with the other plugs still in.

There just is nothing in the intake system that can make noise, except what is on the other side of the intake valves.

Do a compression check. If the intake valves are having a sealing problem, the compression will be low.

If the cam that opens the intake valves is late, you could get a short backward flow just before the valve shuts, which could make some noise.

This is a truly odd complaint you have. But that;s all I can think of that could do this.

check to make sure nor of you vaccum line is not loose and all your clamps are tighten sound line a line is off the system and your intake is not tighten properly

sounds like clutch fan its electronic try unplugging then drive. they are normally loud but this might help with whats making noise.

If there is an engine code po410 you have problems with your airpump. There are bulletins out on this situation.

If the vehicle has a clutch fan, verses an electric fan, sometimes the clutch will spin the fan too fast or at erratic speeds. I'm not saying that's what it is, but just one possible reason. Seeing how you have the warrany, I would take it in and not leave until they have remedied the problem. Let us know how everything turns out and good luck.