1999 S80 T6

I read somewhere in this forum but couldn't find the thread on this. Here's the situation:

When I am accelerating steadily, my car loses power rythemically. For example, at around 2000 RPM while accelerating, the RPM needle suddenly drops to 1700 RPM for a fraction of second and goes to normal (2000 RPM). This happens so quick and abrupt that when you are watching the road, you can feel the power loss, and before you turn your eyes to the dashboard, its back at normal acccerelation RPM. It happens as fast as you can snap your fingers. And... this happens at equal intervals, almost once every 1.5seconds or something, but at exact intervals. Please refer to the image for the example cycle of power loss.

I have no idea why this happens. But, one fine day, it suddenly stopped doing that. There are3 things I did to the car on that fine day:

1. Changed the engine oil (at 3000 miles and I use Castrol Synthetic Blend 5W-30)
2. Replaced the Break Pedal Position Sensor
3. Used Techron fuel system cleaner while filling up the gas

Again, I have no idea which of these 3 factors contributed to a little peace of mind while accelerating (the weird transmission shudder still exists though).

Questions:

Why is this power loss happening? Where is the problem? I am guessing, the engine oil change affected the situation and provided a temporary remedy. Is it true?

Thanks guys.

[IMG]local://upfiles/12401/582EE9BDC6054EFAA048097ED27CD253.jpg[/IMG]

 

my 2000 2.9 was doing the same thing, replaced the brake pedal sensor, all is well now.

 

Hmmm... interesting. I wonder what the faulty brake pedal sensor is doing to trigger this phenomenon.

Thanks, rotgut for the input.

 

I dont really know, odd isnt it, my volvo dealer that I go to happens to have two seasoned techs that are personal friends of mine, I took the car to them and they went right to the brake sensor, anyway, glad you sorted your out, who would have thought.