first check engine timing this is a major cause of vibration in a stationary vehicle, or non firing cylinder could be electrical or mechanical, then harmonic balancer, then look for broken engine mount.
A guitar pickup is wire coiled around a magnet. When the string vibrates, it causes the magnet to vibrate, which creates an electric current in the wire. The signal created by that electric current is then fed into the amplifier which converts it to sound.
Vaccuum leak somewhere
The Idle Speed misadjustment, Timeing misadjustment, or bad throttle position sensor. Search one of the 4WD forums like IH8MUD.com or Pirate4x4 for idle surge. check the coolant level.
Bad lockup clutch in the torque converter possibly.
Check the distibutor model and pickup coil .
A PCV or connecting hose problem can cause great issues with a 1997 Nissan pickup idling. In fact, this can keep it from running, even if it does start, and the engine turns over.
The wiring or electromagnets could be showing their age, a connection might be bad, or the pickup's height adjustment may be getting too low. (The closer the pickup is to the strings, the louder the sound generally is; make sure there is still room for the strings to be pressed, and vibrate clearly.)
Tires are out of balance ( maybe ) A bad u-joint in the driveshaft will cause it too. Check these things.
I have a screeching sound in my pick up when it gets up to 2000 rpms. Does not make the noise while idling and starts fine.
Your mom.
The most likely cause is that it is idling to fast. Try adjusting it down. Then set the timing to the proper specifications and readjust the idle speed. Another thing could be a vacuum leak or a float or fuel level problem.
weak battery or bad alternator.