Rough idle at startup then jet noise and smooths out

[sternamagraph]

07 TB LS 4.2 - In the morning, or after about 8 hours, when i start my TB, the idle is a little rough and gargly, then a noise that sounds like a jet engine kicks in for like 5-7 seconds and when it stops the idle smooths out. its been doing this forever and just wondering if its an issue or normal. i will try to get video today after work if need be.

Thank you for the input.


Chris.

 

[dna59]

I think the jet engine noise would be the secondary air injection pump under the driver side on the chassis.

 

[sternamagraph]

so all this is normal then?

 

[Matt]

Yep. 05+, as far as I know but could be 04 as well, have the SAIS and they all do that.

 

[sternamagraph]

Does it make a difference if I start it up and go? I have a remote starter, so I usually start it while I'm walking to it and it's smoothed out by the time I get in it.

 

[Matt]

Not that I'm aware of. I don't have a remote start, but I get in, start the truck and hit the garage door opener, maybe 10-15 seconds later I'm in gear and heading out.

 

[C-ya]

A co-worker's '09 was making the sound at cool/cold startups. I listened to it one day at break and it was definitely the SAIS pump. It would occasionally set a code. He had it replaced and is much happier not hearing the pump.

 

[AzTruckGuy]

My 03 sometimes does the jet engine sound and then quiets down after warm up....I hate that sound but I guess its normal

 

[Mooseman]

Yes, very normal for both electro-viscous and thermal clutches.

How fan clutches work

 

[C-ya]

07 TB LS 4.2 - In the morning, or after about 8 hours, when i start my TB, the idle is a little rough and gargly, then a noise that sounds like a jet engine kicks in for like 5-7 seconds and when it stops the idle smooths out. its been doing this forever and just wondering if its an issue or normal. i will try to get video today after work if need be.

Thank you for the input.


Chris.

You can unplug the SAIS pump and see if the noise stops. You will most likely get a CEL, but you'll know if that is what it is. It is under the truck on the left side frame rail under the driver's seat position.

 

[Mooseman]

Isn't there a specific fuse for it? Might be easier than unplugging from under the truck.

 

[Mike w]

Mine sounded way worse than a jet