My 94 gmc Sierra 2500 lost power recently and now has a weird whistle sound coming from the engine, but only when I'm in drive driving. It almost sounds like a turbo winding up. My truck don't have 1.
Sounds like possibly a vacuum leak.
Where would the leak generally be coming from is that be the case? I'm just very unfamiliar with this kind of stuff.
Honestly might near anywhere around the top(intake) portion of your engine. Look and listen for loose/broke hoses around the top of the engine. Follow the hiss sound you are hearing. Hose could be the size of a pencil or up to the size of a large thumb.
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