1999 Toyota Camry Carmy stalls when gas padel pressed heavi

Engine stalls if gas padel pressed hard

1999 Toyota Camry 4 cyl Two Wheel Drive Automatic 100k miles

My camry started having this trouble for about one year. It very likely stalls when I drive up a ramp. Before the engine stalls, the engine runs very rough, RPM just dancing and dying out. When it happens, I need wait for 5 min to try to restart the car. Most times, just two or three tries, it will start. During restarting, if I step on the gas padel, the RPM may goes to normal very quickly.

The is no error code when the car is restarted.

In normal situation, the car can be started very easily. If I only step on the gas padel lightly, the car runs at 40 ~ 50 MPH, and it rarely stalls.

I have visited Toyota dealers three times since then. The first dealer suggest replace IAV. I replaced the Idle air control valve in a shop. It was not a fix. Later, friend replaced plugs, plug wire, TPS and fuel filter. The problem is still there. The battery and starter are new.

Is it possible a bad fuel pressure regulator? I searched the Internet, someone experienced similar trouble, a replacement of pressure regulator fixed.

The fuel pump? But the fuel pump works fine if the engine just idle or gas padel just pressed lightly.

Appreciate your help very much.

Regards.