I bought a 2005 S80 with 122k just before Christmas, and my wife loves it. She has put about 3K trouble free miles on it.

I recently changed the oil (sucked it out with a topsider), changed the filter and put in a new air filter. The air filter was after market and didn't fit great, but I got it to clip down. I started it up and it seemed to idle a little rough. I drove it for a bout 2 miles and it stalled going 35 or so. Started up and it seemed OK. Drove it a couple of miles back passed home and it stalled again at about 45. It stalled one more time on the way home, stopped at a light.

The MAF CEL came on a couple of times (but not every time). I disconnected the MAF and it was not perfect but it would idle and drive without stalling. I ordered plugs and a new bosch MAF. Plugs came first so I put those in. After that it even seemed rougher with the MAF plugged in.

I received the MAF yesterday and put it on. Fired right up with rock solid and low idle. Drove two miles to a freeway onramp with a long steep hill and it flew up the hill with lots of power. Turned around and headed home, feeling great. Got to a stop at the bottom of the freeway offramp, and it stalled. Started it up and it would barely idle. Drove it the 2 miles home and it stalled twice more. Let it sit for several hours to cool off to see what that would do. I started it up and it idle as rough as it ever has and I could smell gas (I believe from the tailpipe).

Any ideas what is going on and what I should check for? I am baffled that after each thing I have done it has gotten worse!

 

I figured it out. The air intake that attaches to the the MAF is large and rigid plastic and routes way to the back the engine. I noticed some hoses seemed awfully loose and followed them back to where the attach to that pipe. That pipe should be holding them rigid, but it was completely disconnected and dangling. It is a tough reach from the top, but I was able to press it together enough to start it up and take a short drive, and it was perfect. My guess is that those hoses were losing vacuum when the pipe opened up. I still need to look up how that pipe is properly attached, but that was clearly the issue. Hopefully it is more accessible from underneath and it is not too difficult to properly clamp that pipe.