91 Blazer 4.3/"Y" --> 'chirping' noise from back of engine
 

Yet another strange issue with my new-to-me Blazer...

Working under the hood and can hear a noise originating from the engine near the firewall that sounds like a bird chirping, in roughly half second intervals, likely in rhythm with the RPMs, its not really too high pitched.

but in all my years of driving old crappy cars, this one in new to me.

Any guesses?

The only chirping noise I am familier with is the serpentine belt at the front of the engine. If you are sure it is coming from the rear I do not have any idea of what it could be.

Its not springtime yet so i dont think there is a baby bird in there... :) I did take apart the top of my landlords trailblazer intake and woke up a mouse in his nest, sleeping on top of the valve cover where the spark coil packs are, the thing just looked up at me like "What are you doing disturbing my sleep? Jerk" so I grabbed him in my gloved hand and moved his nest down under the woodpile.

You can use the old screwdriver to the ear trick to narrow down the exact spot the noise is coming from, but my guess is going to be your distributor shaft.

Mine was doing that before and it was my old distributor shaft, when i pulled it out it had some play in it. I put one from the junkyard in and the noise was gone. Take off the distributor cap to get it out of the way and there is a 13MM bolt under the distributor at the 7oclock position that holds it down. Loosen that bolt out quite a bit so you can rotate the retaining clip out of the way, then you can pull the distributor straight up while rotating it to get it out. Make note of where the rotor was pointing to so you can put it back in the right position and make sure you unhooked the 2 wire plugs from the 2 oclock position. You will now have the distributor in your hand and can wiggle it to see if it has any play in the shaft and listen for that noise while you turn it. It should be smooth turning, and have zero play in it side to side. The bushings inside do wear out on them after time.

If you have a manual transmission it's the throwout bearing if you hear it in neutral with the clutch out. If you have an automatic then it probably is the distributor .

the chirping noise has mysteriously disappeared?????