Alright, first this is my daughter & son inlaws car. 1999 S70 with a engine reving problem. Happened to them once while just the cruise control on. Stopped vehicle, shut it off, turned it on, ran good. Then happened (or happens) when A/C on...Vehicle seems to be in limp mode (from how they described it) when this happens. Any ideas besides get full coverage and report it stolen?

 

It is 100% normal for the engine to rev slightly (some vehicles you can feel it) when the A/C compressor ends a cycle and kicks off you a few seconds and then back on.

It is also normal that when the A/C is compressor running or "on" that you can get up to 50 HP loss. Enough to feel if you don't use a/c much or haven't for awhile.

But you didn't explain your "revving" problem.

 

Hey Joe, I don't under stand the problem either. Does it stall while cruising? Does it just shut off on them? Is there a CEL?