Chirp at start or shut off...
 

Sometimes my engine makes a chirp sound when I start it (usually when it's cold) and sometimes when I turn it off...

anyone know what might cause this?

I had a chirp and it turned out to be a vacuum hose. It was the cheap silicone hose I bought at Autozone. Walls of the hose were thin and would suck/collapse and give the 'chirp' sound. It was one hose around the solenoid mess that had one of those green/white check vavles connected to it. I found it using a stethescope.

You're kidding? I would have never guessed it would be something like that...

I find it hard to believe, actually... although it does make sense in a way.

Was that hose also causing a vacuum leak?