Porcelain broke

While taking the spark plugs out of my trailblazer, the porceline broke and then fell into the cyl. How do I get it back out?

Welcome to AF. How big is this piece, this should disintegrate when started, there is no way to get it out, you could spin the engine over, not starting it, plug out and hope the compression blows it out the plug hole, maybe.

If the porcelain below the plug shell broke and fell in, DON'T move the engine.

If the spark plug now looks like this but with the lower half of the porcelain and center electrode missing, DON'T move the engine:

http://72.19.213.157/files/ACSparkPlug3.jpg

You MAY be able to fish out the piece with a strong magnet on a wire if the electrode has enough iron, or may be able to get it with very small pickup fingers - Maybe. You should at least use a bore scope and investigate the part(s) left in the cylinder.

If a meaningful sized piece of porcelain is left in the engine, it can do serious damage. If very small pieces are left in the engine, they can lodge between the the margin of the piston (above the top ring) and cylinder wall and eat the cylinder wall raw, ruining rings, pistons, and possibly the block.

Personally, I would use a bore scope to look and possibly try to retrieve whatever pieces are left that, or pull the head. If it weren't my engine, I might do something different.

Im afraid you will have to pull the head.