The idling speed on my Mazda 323 oscillates (going up and down) between 1000 and 800 RPM when the engine is at running temperature. It does not do that when the engine is cold. If I set the idling at 700 RPM when cold, the car will die when it is hot. What could cause this ? The car runs fine otherwise. The timing is corrected at 700 RPM.

Thanks.

 

Your may need to rebuild yer distributor, but before that check all your vacuum lines, ignition components, TPS sensor, O2 sensor etc and make sure everything is connected and/or not worn out.

It's hard to trouble shoot problems like these over the internet, because oscilating idle rpm can be caused by quite a few different things. plus it helps to know the year/model of yer car.

 

My car is 1993 Mazda 323.

 

In addition to Awal's suggestions check the air intake hose for cracks, clean the throttle body, and clean the EGR system. That includes the nipple for the vacuum hose to the EGR boost sensor. It often gets plugged by deposits.

 

I cannot locate the EGR in my car. I have checked the MAF, TPS, O2 per Hayne manual and they are OK. Enclose are couple pictures of the engine.

 

Enclose is the vacuum routing diagram, there is no EGR but there is an Purge CV. Could that cause the oscillation problem ? How do I check the Purge CV ?

 

Maybe you don't have an EGR. Are you in the USA? In the USA your model is called "Protege".

If you have an EGR you would find it under the throttle body. There would be a steel pipe routing from the exhaust manifold around the engine to the EGR valve. The vavle would be attached to the Intake Manifold. If you take off the rubber intake hose you should be able to see what I described.
If you don't have an EGR you have fewer problems to content with.
The Haynes manual will tell you many test procedures in the front section of the book, that includes the PCV. Pull it off and shake it. Do you hear a ball rattle? That's a good sign. Clean it with throttle body cleaner and reinstall.
Since your car is 19 years old you have to expect that rubber parts are hardened, cracked and braking apart. Inspect that intake hose by bending it. Cracks develop in the rippled section.
I think you have a vacuum leak and the computer is struggling find a steady idle.