Mazda 626 Engine Rpm goes up and down. ?

Idle Rpm usually must be 750 but this goes upto 1500 Most of the time. At start, traffic lights, etc..

As it is a manual when I force the engine to slow down by pressing the brake and giving the clutch when it is in gear, it comes back to normal rpm and stays constant at 750rpm.

What do you think?

when was your last tune up? Check air cleaner, fuel filter, and plugs for starters.

When the engine comes down to 750 RPM because you're dragging the clutch, the only thing you're doing is burning your clutch plate up. Most probably the problem is you have a vacuum leak or an EGR valve which may be sticking. Have your car identified and quit riding your clutch.

I propose you to chech and fix your air filters and service it.

Brian W is correct, go with it

Many concerns can because a surge like this as well as a failed idle control componet[a motor or vacuume valve that controls the idle speed of the engine or a problem with a fuel injector dripping I remeber when I was a kid I had a 87 mercury topaz and it could run the range of rpms I replaced the idle control motor on the side on the engine twice[they where a common problem and I had a fuel injector leaking a just amount of fuel down the intake causeing the engie rpms to change between 500 2000rpm. pay a mechanic one hour too look the car over and give you a diagnosis. it will be cheaper than a new engine or a clutch substitute

i could go with John m

I'm with BRIAN W, EGR. Had the same issue. it is code 16 on the computer.