engine starts but then dies a couple seconds later

Hello,

This issue can be due to lack of fuel or air.
If the fuel pressure does not stay constant after startup the engine will stall, regardless of you pressing the throttle.
If the fuel pressure regulator cannot keep proper pressure to the injectors the engine might start but will stall afterwards.
Check the fuel pressure at the rails. The pressure check port is located on the right hand side fuel rail. You should be able to rent fuel pressure test gauge from you local auto parts store.
This vehicle should have 26-30 PSI of fuel pressure.

Here is a helpful video:

https://youtu.be/aITQclp7zIE

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Also if you have a large vacuum leak the engine will not run as well. Check all the hoses under the hood for any damages or cracks.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

I have attached diagrams for your reference.

Please let me know of any questions.
Thank you.