My mechanic gave this thing. i can put were the spark plug goes into. then i blow on it and if air comes out somehow, somethings wrong. is that true? oh yeah the rockers aren't on
Does it have a gauge on it for air psi and a connection for an air compressor? If so it sounds like a cylinder leak-down test. It'd be funny if it was just a plastic tube that you physically blow into, you'd have to video tape that and send it so we can all laugh
Someone please correct me if I'm wrong but I think you want the piston at BDC and thread the tool in the spark plug hole, then blow compressed air into the cylinder and see how quickly the pressure drops. Then you can listen if the air comes out the exhaust port, intake or down the crankcase.