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Is the check engine light staying on when the engine is running? If it is, have the computer scanned for diagnostic trouble codes. Most parts stores will do it for free or lend/rent you a scanner.
If that isn't the case, many things can cause this, but my first suspect is fuel pressure. I am basing that on your description. In this case, I would suggest checking fuel pressure. There could be an issue with the pump or even a partially plugged fuel filter. It seems that at first start, pressure may be low and then slowly reach spec.
Here is a link that shows how to check pressure:
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
Here are the manufacture's specifications for fuel pressure:
PRESSURE, VACUUM AND TEMPERATURE
Ignition ON, engine OFF .................... 345-690 kPa (50-100 psi)
Relieve the fuel pressure to 69 kPa (10 psi). Verify that the fuel pressure does not decrease more than 14 kPa (2 psi) in 5 min
I realize most people don't own a fuel pressure gauge, but most parts stores will lend or rent one to you.
Let me know what you find.
Joe
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Saturday, September 21st, 2019 AT 8:45 PM