91 mazda 323 wont rev out past 2500~3000rpm or idle

I would think that your Carburator needs to be inspected and cleaned. There are some parts that wear but what is happening is you have an Air Leak on the Carb itself

When does is rev high and low? If it does this at idle check for a vacuum leak or maybe a blocked airflow

CHECK THE TEMPERATURE AND OXYGEN SENSOR

Sounds like you have a vacum leak. Trace the vacum lines under the hood to locate broken or uninstalled vacum line.You can always spray a little brake cleaner in suspect area ,and if the idle goes up, you are close to the problem. Even a intake gasket leak will cause high idle

I have seen many of these die out due to a broken or cracked vacum hose. Look under the hood and listen for a whistling or hi vacum noise. You can also take carb cleaner and spray around vacum hose and pcv valve and intake. If the motor revs up or stalls out when you do this then you definitl have a vacum leak. Find and replace.

If I am wrong about the vacum hose I woulds inspect idle air control motor, throttle position sensor, (both canbe cleaned as a temporary fix) or worst case may be a fuel pump.

if its carby engine has the idle solenoid stopped working or lost power very common
single wire soleniod can be checked for power with test light
power=ign. on/run
no power=off/no idle
or has some one adjusted carby settings?

some vacumn lines only **** air when the antifreeze warms up,i would check either EGR valve or EGR sensor,then the fuel pressure regulator,but if you think its a vacumn issue,then spray carb cleaner around the throttle body and lines

check your idle air control valve and also check to see if your low on antifreeze.

sounds like u have a vacum leak spray vacum hoses with carb cleaner and when motor revs up thats the hose with the leak fix hose and see what hapens

if it trys to turn over spray starter fluid to the carb. it might start then