4 Wheel Drive/SUVs: 1987 jeep cherokee, throttle position sensor, windsheild wiper

Question
i own a 1987 jeep cherokee pioneer 4x4. 6 cylinder. sometimes (not all the time) when i start my truck, it seems like its not idleing out right. its a little hard to explain. you know when you start it, it revs up, but sometimes that reving sound doesnt go back to normal, it will just stay reving up, if that makes sense. also, when im driving, and i hit a bump, sometimes the car will jump a couple times afterwards. one time it actually died. what could be causing these things to happen? any help you can give me would be wonderful. ive had a couple people look it about the ideling problem, but they dont now what it is. also, my rear windsheild wiper doesnt work. is this something cheap or easy to fix? i can here the motor turn on but the wiper doesnt actually do anything.

Answer
Tina,

The idling problem sounds like a vacuum leak.  You can look under the hood, and see if there are any loose or disconnected vacuum lines.  Another way to check for a vacuum leak, is to spray some carburetor cleaner lightly around the engine while it is running.  If you have a vacuum leak, many times this will cause the engine idle to change when you spray near the leak.  This is the most common cause of idle problems.
There are other components that can cause this, such as a throttle position sensor, idle speed motor to name a couple.

As far as the rear wiper goes, you need to go to the rear of the Jeep, with it turned on, and see if you can feel the wiper trying to turn.  If the wiper motor is running, and the blade isn't moving, there is a chance that the internal gear drive has broken.  If this is the case, the wiper motor would need to be replaced.

Carl