99 Chevrolet Lumina – Weird Starting Issue

My 99 Chevrolet Lumina with a 3.1 engine is having problems starting. When I try to start the engine, turning the ignition key normally, it will crank normally for maybe two seconds, but then the cranking will slowly fade and the starter will grind on the flywheel. It’s as if the engine is starving for air during the last part of the starting process. Also, sometimes during an attempted start, the PCV hose will blow off the PCV valve.

I’ve checked and cleaned the PCV valve and hose. Also, checked the air cleaner and snorkel tube, and these seemed fine.

The only way I can get the engine to start is to precisely turn the ignition key for around a half second. If I turn the ignition key any less or any more than a half second the engine will not start. Because the cranking time is so precise, it might take me five or six tries to start the engine. But, when the engine does start it runs normally with no check engine light… Are there any other parts of the starting system I can look at that might be causing the problem? Thanks!