check the tensioner pully.
heres how.

First, go to the auto parts store or a bearing shop and get a 6301 sealed bearing.(about $5.00)

Now go home and get the following tools,
hammer, 3/8" ratchet, 15MM socket, 3/8" extenion, spring clip removal tool, or a small regular screwdriver

Pull off your belt(or in your case, rev the motor until it falls off)
grab the pully and wiggle it. If it moves in any direction other than the intended rotation, the bearing is NFG, I am talking even 1/2 of a MM.

Simply unbolt the pully slide it twards the rear of the car and it slip right out of the bracket.

Next you need to remove the pully from the threaded shaft it rides on. use that hammer, one decent hit should knock it loose and you can pull it out.

Next remove the spring clip that hold the bearing inplace.

After that,knock the bearing out of the pully. Place it on its side,(spring clip side down) use the 3/8" socket extension placed on the bearing. Use a hammer and give it a solid couple of wacks. The bearing will pop right out.

Once the bearing is out of the pully, clean the pully up with a rag or paper towel.

The new bearing needs to be "press" fitted into the pully. that is simple. Carefully use your hammer and that 3/8" extension. Mind the seal, you dont want ruin the seal or youll be doing this again in a few months.

Once the bearing is in the pully, replace the spring clip, the threaded shaft. Slip it back onto the motor, repace the belt and tighten everything down.

Start your motor up and notice how much more quiet the motor sounds now that the spent bearing has been repalced

This job takes about 15 minutes to comlpete

Tom