I have 97 protege automatic transmission when i runing the a/c and head light it stalling the engine.rpm goes up and down and than stall the engine.i have to keep my foot on gas padel to keep it from stalling and also got a check engine light of P0400.does the P400 cause stalling problem?

 

Yes that is an EGR valve malfunction. Remove and clean the EGR and ports. Check all hoses to it and make sure the EGR valve has no vacuum to it at idle.

 

https://www.mazdaforum.com/m_36162/tm.htm

Followthe link to post from Babyhuey. This helped me out with the same problem cleaning out the vacuum ports might help. Read both pages. The pics are helpful too. It's a pain in the butt job if you have a 1.8L, But it's the best place to start.