98 Mazda 626 AC or Engine problem. Please help

[wwpaulww]

My 98 Mazda has a engine problem while operating the AC.

Everything is fine when it's driving at high speed. Problem comes when parking or driving at low speed (say<15mph).

The problem is that, with the AC on, the engine "jumps" (shakes very seriously) every 2 seconds. With the jump, the RPM of the engine drops seriously too. At parking, it drops from about 700 RPM to 400RPM or even lower. The AC is still cooling though.

Thank you very much for your help.

I took good care of it, and oil change on time.

Some works have done recently to my car:
Timing belt changed.
Tune-up: change the sparks, wires, PCV valve, fuel filter, air filter.

[Mark E M]

There is an idle step-up solinoid that kicks in when the a/c is turned on yours is not working. Have that checked out. Hope this helps.Later Mark.

[wwpaulww]

Thanks Mark. I'll go get it check.