If it is stalling at high speed and hard to start, that sounds like a fuel pressure issue. Have you checked pressure to see if it is within the manufacturer's specs?
Also, if it stalling at high speed, how do the RPM's not move? Please explain.
As far as the fuel pressure, here is a link that shows how it's done:
Here are the specifications for pressure. The attached pic explains the causes for variation.
2013 Hyundai Accent L4-1.6L
Pressure, Vacuum and Temperature
Vehicle Powertrain Management Fuel Delivery and Air Induction Fuel Pump Fuel Pressure Specifications Pressure, Vacuum and Temperature
PRESSURE, VACUUM AND TEMPERATURE
Start the engine and measure the fuel pressure at idle.
Fuel Pressure: .................... 429 - 469 kPa (4.38 - 4.79 kgf/cm2, 62.3 - 68.1 psi)
NOTE: If the fuel pressure differs from the standard value, repair or replace the related part.
Let me know if this helps. Also, let me know if the check engine light is staying on when the engine is running.
Take care and God Bless,
Wednesday, February 17th, 2021 AT 5:46 PM