Replaced catalytic converter and O2 sensors

Have the fuel pressure checked. That could be the isssue and make sure the intake does not have any obstructions.

Why did you replace this? Who told you it was bad?

Expensive guess.

Anyway, is there a check engine light?

Start with fuel pressure test.

Roy

What was the code? Codes never identify bad parts, just failed systems.

A 420 code is a cat effiency code and yes, the cat would be bad but is not the issue you have

Roy

They re set it and it is a 3 trip failure. It may or may not come back on but it will not tell you anything about your current issue.

Look for vacuum leaks, it may be a hose off tht will make the car not idle. Otherwise the idle air control may be the issue

Roy

Good luck

Roy