my friends brother has a 1989 cherokee with 4wd 4.0 and it is idling fast and he thinks it is a vacume leak. do any of you know andy common things to cheack for this year?

Mmm... search.. =

http://www.automotiveforums.com/vbulletin/showthread.php?t=141449&highlight=fast+idle

he had replaced on sensor and it fixed the idle problem then he shut car off after he tried the sensor and when he started it back up it went into a high idle. this could be the sensor.