This is my first post on this forum!
I'm having a problem with my 2002 s80 2.9 liter. (non turbo) upon acceleration,(usually hard acceleration. half throttle or more) my car hesitates and looses power for about a second and then regains it. it only does this when accelerating from a dead stop or below 20 mph. When I push the accelerator down the car will speed up for about 1-2 seconds, then the rpms will drop and acceleration will stop for about a second, then accelerates normal, and does it again. every 5 mph or so until about 30 mph, then it accelerates normal. its like the power completely cuts off for a few seconds and then kicks back in again. this is really annoying because when I merge into a fast moving road, the car takes a lot longer to speed up because of this hesitation. any ideas what could be causing this?

 

Anyone?

 

The the idle drop down a lot when coming to a stop? Are any lights on your dash lit up?

 

Idle is normal.
An yes, the check engine light is on, but it had bee on there for about a month. I think it went on when I drove without the gas cap. It was on before this problem

 

You might want to start there. Go somewhere and get the xlcodes checked