Toyota Repair: High Idle on a 93 toyota 4 runner, toyota 4 runner, oxygen sensor

Question
Dear Ted,
I have a 1993 Toyota 4 runner v6 3.0L.5sp4x4. Lately my idle has gone from 1000 rpm to almost 2,000 rpm until it is warm then it will drop to 1100 rpm,before it would idle about 800rpm when it's warm. The only error code I have received is code 25 which is running lean, but the check light will go off after some miles, but the idle doesn't change, it does how ever change in sound when it seems normal idle drop is done , but the idle doesn't drop, but sounds smoother. Any suggestions on what to test or where to start. Before this started to happen the idle was about 1100rpm cold and 800rpm normal(warm). Any suggestions on what to test or where to start.

Answer
Check the throttle body plate to meake sure it's closing all the way. Clean the inside of it if there is a lot of carbon deposits. Check for any loose, cracked or disconnected vacuum hoses. The reason for the code 25 is that the oxygen sensor is seeing too much oxygen in the exhaust.