Chosen Solution
When my 2007 Sentra reaches 40mph, the RPM’s drop to 2 and the car whines, but will still accelerate. Just recently changed the catalytic converter. Could this be a transmission issue, or just a sensor.
if your saying your car wont go past 40mph then the key you might be using is a valet key it prevens somebody from going over 40mph . he purpose was if a hotel worker asked you if he should drive and park our car you would give him that key so if he tried to steal tha car he could not get far
It could be a plugged catalytic converter. I had that happen to me when I seafoamed the car. It was either a plugged cat or perhaps something with the VVT not switching cams at higher speed. It resolved itself on my car spontaneously. I could not find very much on it online. Hope you got it worked out!
