Starting issues

[Zooey32]

Ive been having issues with my car recently its a '91 300zx NA. When i start it up it makes a high pitch screech sound, the car feels likes its gonna shut off its jumpy and cant turn on head light and put windows down without my rpms dropping. heres a video i took to shiw you guys an example sorry for the quality. https://www.youtube.com/watch?v=RB4m2BhcnsQ

[denraweb]

Ive been having issues with my car recently its a '91 300zx NA. When i start it up it makes a high pitch screech sound, the car feels likes its gonna shut off its jumpy and cant turn on head light and put windows down without my rpms dropping. heres a video i took to shiw you guys an example sorry for the quality. https://www.youtube.com/watch?v=RB4m2BhcnsQ

That sounds like an alternator problem to me. The pulley has bearings inside, and rarely, but possible, they can wear out and make it harder to turn the pulley. The screech is the drive belt. For the reason mentioned above, or something else, the belt is slipping on the pulley. When soft stretchy rubber slides on smooth shiny metal, it will make that noise. Think of nikes on a clean hard floor.

Same noise comes from a loose belt. Now it could be your belt is old and needs to be replaced, and the pulley being fine. That would mean the alternator needs to be replaced regardless. If they pulley is locking up, the reason your RPM drops so much would be because the alternator isn't spinning enough and can't produce as much power.

Go to an auto parts store that does free testing and have them test the alternator. They will tell you if it's not charging correctly. A step further would be to remove the belt on the alternator and with the engine off you should be able to spin the pulley on the alternator by hand and it should spin freely like a skateboard or roller blade wheel. The noise could also just be from the power steering, and just coincidence that you have a bad alternator at the same time.

Bottom line: The noise is from an accessory belt being too lose/tight or sliding on the pulley instead of actually spinning it.

Bottom line 2: Your alternator, for reasons currently unknown, isn't kicking up enought amps to power everything and keep the car running. Could be faulty/bad alternator. Or faulty/sticky pulley that needs to be changed.

Inspect:
-All drive/accessory belts
-All pulleys; remove belts to do this (AC, Power steering, alternator, tensioners) (minus the crank pulley of course since this is stationary to the engine)

[Zooey32]

Well the alternator has been replaced less than a month ago. my crank pulley was just replaced a month ago the old one had shifted and cracked. The mechanic who replaced it told me that my crankshaft had been grinded by the broken pulley and that the new one would be loose and wobbly.

[denraweb]

Well the alternator has been replaced less than a month ago. my crank pulley was just replaced a month ago the old one had shifted and cracked. The mechanic who replaced it told me that my crankshaft had been grinded by the broken pulley and that the new one would be loose and wobbly.

Well like I said, that noise is from an accessory belt slipping on one of the pulleys. So check which pulley is creating that. You can remove the power steering belt, start the car and see if the sound is still there. If it is, put the power steering belt back on and remove the alternator belt and start the car. Keep in mind while the alternator will not be rotating, the engine will be running solely on battery power which will drain your batter quickly if you let it run. Just start it, see if the sound is there, and then shut it off. Check that way to see which belt is the issue. Once you know which it is it will make it easier to pinpoint where the issue is coming from.