Hi, I am new here so I hope I am doing this right. I have a Volvo S80 SE 170Bhp which has an intermittent fault. At approx 70Mph it suddenly loses power and drops to around 40mph. Pressing the accelerator pedal will not produce any acceleration. When pulled over and stationary the engine continues to run but is very lumpy as if only going on a couple of cylinders. If the engine is turned off for a period of around 5-10 minits the car starts and performs normally. The fault may not appear for several days or longer. The Volvo garage can find nothing wrong with the car, no error codes in the system and can not so far make the car do the same thing under road testing. Sometimes when the car is pulled over the engine will rise on its own to around 3000 revs and then drop to 1500, rising again to 3000 and dropping once more. Can anyone help? Please?

Have you had the throttle body cleaned?

If not have it done and it should fix it.

I believe that you're experiencing this:
http://www.bba-reman.com/volvo_throttle_actuator.htm
I've had experience of this recently in my 2001 2.4 petrol at 55,000 miles.
The solution is to have your dealer clean the Marelli ETM unit.
There may be mileage in getting Volvo to pay for this.
I haven't tried to get reimbursementyet,
but I will be pursuing it having seen this:
http://www.arb.ca.gov/newsrel/nr112205.htm
Hope this helps. :57:

Actually i understand how you can feel, i had exactly the some problem on my S80 T6 about 2 weeks ago, and the problem was the cumputer of the Throttle Body.

The repair cost is 1 500$, and guess what, you're luky.. just like i'am. They's a recall on that part, and it'will cost you 0$, Volvo cover the charges.

So just take it to a Volvo dealer, it'll take maximum of 5 hours to repair and you car will run as a new.

Regards