Cat question

[WongFeiHung]

Can a bad catalytic converter effect idling or cause stumbling?

[twitchy]

theoretically yea

but when i cut mine off, no difference at all. When i re-installed it later on, same thing, no change..

likely something else

search out idle problems

[thx247]

no it can't it. The cat does not influence the engine operation at all, only smog emissions

[gfisch]

If it were rusted though or broken, absolutely.
It would definitely effect the engine.
When mine broke when I ran over something, the car just wanted to stall out. Had almost no low end torque.