I own a 98 maxima and recently I noticed the tachometer rmp drop too fast from 2000 to 500 or below when the gas pedal is released. Any body knows why

 

I'd check your TB/IACV. They could be overdue for a good cleaning.

 

"tachometer" is not a thread title, it's single word. I've revised it to something more appropriate

https://maxima.org/forums/4th-genera...e-contest.html

 

I've had this happen to me on two different occasions. First one was the IACV going bad. Second time was an O2 sensor. If I let off the gas over 3k rpms, the engine would actually die. I had to tap the gas on the way down to keep it alive. Only happened while warm. I had a O2 sensor code so I knew what it was. When I went to replace it, the wires were broke off the sensor.