I recently purchased my 3rd Ranger, a 1998 2wd with a 2.5, 5spd. When I bought it, it would not run on high idle when cold, but would run great after it warmed up. I talked to a mechanic friend of mine and he told me to clean the idle air control valve and the problem may go away. I cleaned it and it ran at 2000 to 2500 rpm all the time, so I bought a new one and installed it and still have the same problem, any ideas?

 

Mass Airflow Sensor. get some rubbing alcohol and just kinda dump it on there.

 

first clean the mass air meter with some carb cleaner.. did you also check for vacuum leaks?