1999 Hyundai Tiburon - Low idle and stalling

My diesel engine d4bh idle goes too low then stalls when I turn on the AC. What causes this?

The engine is supposed to compensate for the extra load of the A/C compressor when you run the A/C. Yours isn’t and it’s causing the engine to stall. Has the check engine light come on? If so, have you had the code checked?

To the best of my knowledge the Tiburon was never made with a diesel.
More information please.

I see no diesel engine option for a 1999 Tiburon either. Are you outside the USA OP?

Hyundai made a diesel van called the Starex for the Pacific market during that time frame. That’s my best guess as to what the OP is referencing.

Should we really have to guess in regard to the vehicle in question?
Even if the pull-down menu doesn’t include the OP’s vehicle model, that info could have been included in the body of his post.

No, it shouldn’t be necessary to guess but the problem isn’t vehicle specific. The A/C compressor is causing the engine to stall.

… or it could be a problem related to the IAC… assuming that a diesel engine has an IAC…

Yes. I said in my original reply that the engine isn’t compensating for the additional load of the A/C compressor. A faulty IAC or ECM would cause that.