Why can some cars adjust the throttle opening and some cars can't?

The machine can be adjusted electrically, but not with a computer board. However, there are other reasons to solve the problem of unstable idling. Adjusting the idle speed alone not only affects the fuel consumption, but also affects the engine. I don't know how many kilometers you have, about 5 W. Go to a professional place to check the carbon deposition of spark plugs and replace or clean them as appropriate. I hope it works for you!