I have a 2000 S70 GLT SE Turbo. It's been running well after various recent part replacements (including alternator, heater core, antenna ring and leaking repairs). My only concern is that when the car is in neutral the tachometer jumps one or two notches up. For example, it will be a notch below 1 on the tachometer when in neutral, but sometimes it will go up and down between that notch and the 1. It isn't a significant amount, but there is a revving sound that goes along with it. It also happens when I am stopped at a stoplight.


Also I should note, it's gotten worse for the past year.

Just trying to make sure I stop a problem before it gets worse. Thanks for your help in advance!

 

That is likely some type of issue with fuel metering. Probably related to a dirty MAF. The hunt could also be from the O2 sensors but I doubt that since I would expect a code before it got that severe. Hunting is the inability of the engine to compensate for changes in air/fuel and speed, etc.