i have changed 3 oxygen sensors volvo s80 not running well yet ....?

First why only 3 O2 sensors there is 4 on a 6 cylinder or 2 on the 5 cylinder There was a 5 cylinder turbo and a twin turbo 6 cylinder. Without the codes listed I am not sure what you are trying to fix. If its surging its in the throttle body . That should be covered under Volvo's 10 year 200,000 mile warranty on that part they extended it several years ago, It could be a vac leak , or a software issue. If its a miss it could be several other things. The list is endless . PLease be more specific with your questions and give a little more detail on the problem and someone will definitely try to help you. I also can try to help you thru Marcomotors.com

You could have one of the 8 coil packs bad. Sould be so many things with an S80! I own an S80T6, 2000 model and without having the ECU read by Vidas at the dealer, your spending money you may not need to spend. I had a weak coil firing one of the plugs, not causing a miss and it ran like a kiddy car, no power, slow response, etc.Take it to the dealer and have it hooked up to the Vidas and go from there!

It's hard to answer this question without knowing the year of the vehicle. If you've already swapped out 3 oxygen sensors then it's obvious something else is wrong. You may have either a bad catalytic converter or a bad chip in your car's emissions controls command unit (I forget the exact term Volvo uses for that but it's the black box that has the processors, and all the leads for the emissions control system run back to it).

The error code may take a while to clear out with out a reset.

Don't be surprised if the new sensors do not correct the problem. There may be an exhaust leak, intake leak or a fuel problem at the root of the error. Not knowing the ignition system well, but guessing, it could be bad plug wires.

Yes, they need a good trip.