My 2000 volvo s80 rough idles up and down how can i fix this? When I stop or just sit in neutral my volvos idle goes up and down. The car also doesn't have a good pick up speed, it seems to struggle when i press the gas pedal. I just had an oil change. What causes this and how can I fix it?

The car has no idle valve. This is a typlical characteristic of a bad throttle module. Be careful cleaning this module! DO NOT spray anything directly into it. Wet a cloth and wipe it. It rarely helps but unless it is a turbo it is easy to get to. BTW a new module dloes require software.

Have the idle air control valve checked, it might just need a cleaning, or a new one. Check all the vaccum hoses for leaks, all it takes is a pin hole to screw up the sensors.

First did problem start after oil change if it did wrong grade oil will have been used too thick effects hydraulic valve lifters if not since oil change remove throttle body clean well and refitl