Here's a great link to error codes for w3wp (event id 1009) and what they likely mean:
My current issue is error 0x0 which is documented in this link but fairly sparse. I checked the debugger flags with gflags and everything was unchecked. I'm still looking for a resolution to my issue.
I did find a resolution to this issue. I went through all the configs and our DRP (Disaster Recovery Procedure) document to see if a could figure it out. No dice there. I downloaded and hooked up procmon to see if it would tell me which registry key or file was causing the issue. No dice there either. It turned out that since our app had a dependency on SoftArtisan's FileUpEe, the fileUpEe dll's were registered in the wrong order! I had registered them 'com' folder first, 'dotnet' folder second (per the DRP). They needed to be registered 'dotnet' first and 'com' second. That made my IIS appPool stop cratering (it was definitely the issue).