1994 jeep has a whinning noise

Typically not the tensioner usually that will just become weak, the wining comes from 2 different items and the easiest to change is the top pulley can't remember the technical name for it. But the bearing goes bad in that creating a whine the other is your power steering pump. Usually you can tell if it is that by starting the engine and turning the wheel at a stop. Try the top pulley first. Take the fan belt off, one bolt in the center of the pulley and pull it off.

check alt bearing,open hood & listen while running,turn off engine and remove drive belt then start engine to see if noise goes away.

are you sure the noise is comming from pump and not the belt tension pulley right next to it ?

I use a wiffle ball bat with both end caps cut off (hollow tube) held to my ear to help localize noises on running engines I have even found tricky intake vac leaks with that trick

You can try "belt dressing." You need to make sure that its the belt thats making the noise.

i have thought about this,and trying to put this in my mind.and say the tensioner should not move and should most deffently not make any noise it should be silent .is this the right part?the main thing here is the allingment im have a go and saying have you the wrong belt?and you should not have a whinning noise as this susegests a bad bearing i dont think you are far away from the answer?tensioner or belt.adrian ,,,

May be a bad bearing on belt tensioner or idler pully

your right as rain

Its not the computer its the EGR valve actulator de-energizing. Nothing to worry about unless your check engine light comes on.

I had the same problem on my 2005 Envoy. Turned out to be the idler pulley bearing. It is just a pulley the belt rides on. The bearing in the pulley was what was making the high pitched whine. I replaced the bearing, and the noise went away.

If it gets worse when turning the wheel at a stop, then it's the power steering pump. Could be the power steering fluid also. Check your belts for wear or damage. The idle pulley will make a constant noise, sometimes whining sometime screeching. To check idler pulley it is best to remove belts.