Team, I have an 08 S40 (2.4i auto trans) that I cant quite figure the cause for a couple of issues. I think it mucht be the AC system but not sure. When using the AC I sometimes get a check engine light and the P0171. I had already changed the MAF with a volvo OEM. Also, on occasions while using the AC it Stalls and loses power. Not enough to stall out but it wont move almost like a tranny slip (this seems to happen in hot weather). I was getting the check engine light fairly reguarly, but I stopped using the AC and havent had either issue since.


Any thoughts?

 

The only way your AC is going to affect anything with your engine is by giving it a slightly higher load. If your engine is running lumpy, the extra load might be enough to make it noticeably worse.

The P0171 error can point to a number of things, including a fuel system issue, vacuum leak, O2 sensor problem, etc.