Whistling Sound Around Throttle Body

[mikeC8]

97 Sierra K1500, 5.7 liter. High pitched whistling sound underhood in the vacinity of the throttle body. Starts after truck warms up and quiets down when accelerating. I've wiggled hoses, disconnected what I could without stalling engine, checked air lines into throttle body, checked air filter, etc. Sound does not change when I apply brakes so I don't think it's related to master cyclinder. The only time it changes is when I accelerate, then only gets quiet until I come back to steady speed.

Truck has 85,000, runs great. No codes.

I read some of the other forum posts about whistling but couldn't fine one with similar symptoms.

Any ideas? Thanks........Mike

[maxwedge]

Sounds like a throttle bdy gasket, spray carb cleaner around the base see if it changes.

[danielsatur]

Do a Google '' Youtube DIY Auto scotty cigar'' , a smoke test is used to pinpoint any unwanted air leaks.

Caution - don't be smoking near carb cleaner, or starting fluids.

I like using smoke, it's done with the engine off, safer, and not harsh on gaskets.

[mikeC8]

Originally Posted by maxwedge

Sounds like a throttle bdy gasket, spray carb cleaner around the base see if it changes.

Thanks. I went out and tried that and couldn't detect a difference in the sound. I also sprayed around the connection points for the hoses. I'm guessing that it is vacuum related since it stops or quietens down when I accerlerate. Also seems temp related since it doesn't start until I've been on the road for about 5 minutes or longer.

[pluman77]

I have the same problem with my 1999 2 door tahoe. 350 vortec all stock aside from wheels and tires and tinted windows. it is a 2 wheel drive pregnant corvett.
it doesnt start when first fired off, it starts after about 1 or 2 minuets. at half throttle it isn't there but I would be going way to fast way to qwick if I had the gas p down all the time.
at idle it is just like a turbo spooling and just a little gas and it gets higher pitched. it is running perfect, I took it to the drag strip and tested to see if it has slowed it down and it ran with in 2 tenths of a seccond of what I poasted befor. last summer I layed down an 11.62 for a best, and the 3 passes I made this weekend were 11.75, 11.68, 11.81 so it doesnt seem to affect performance. it just drives me nuts!!!!!!!
I have damn near pulled the top end from the motor and didnt find anything out of place cracked or missing.
oh yea, when I shut it off it continues to wistle for 1 1/2 to 2 sec after the key has been turned off. that is how I first noticed it.

[pluman77]

That is an intresting thery but I replaced the exaust from the manifolds back back in 2010.
I will cjeck the exaust manifold gaskets amd let you know

[swingline]

try cleaning the throttle body and iac port. probably just normal carbon build up.