I have a 97 850 glt, I just replaced the PCV system and cleaned the IAC while I was doing it. I had some codes before replacing the PCV and now those are gone. The new codes I have aren't the same as the old codes.

I am getting a P1505 and P1507 with a slightly rough idle. Should I take the IAC off again and try to clean it better?

 

wondering if you ever figured out a solution/reason for you problem. Having similar symptoms.

 

Check all of the vacuum lines for leaks

 

+1 on looking for vacuum leaks and intake air leaks. Keep in mind, the PCV system uses the vacuum to capture/burn the blowby emissions so you may have something going on with those hoses or with the oil separator. Probably requires a smoke test on both the vacuum lines as well as the intake air path.

See this thread: https://www.matthewsvolvosite.com/fo...ic.php?t=82766

 

Turned out to be the MAF sensor. Popped a new one in and it's back to normal.