Thanks to advice from this board, I fixed my rough idle problem a few weeks ago by changing the ignition coils, but I've noticed a new problem recently. The car runs fine most of the time, but there's a problem when I try to accelerate aggressively (freeway merging, passing, etc. that's heavy on the gas pedal). The car will "stick" at whatever speed and rpm it happens to be at and will start to shudder. If I let off the gas and accelerate gradually, everything seems fine again. I don't get any warning lights either. Any thoughts?

 

What year is your car?
Have you had any software updates done lately?

 

I apologize if my question is off the topic. but I want to know where the ignition coils located? I have s40 2001? any answer will be appreciated. Thanks.
btw, I have the same problem with my accel. I might bring my car to a local mechanic or something.

 

The coils are located under the plastic cover on the top of the engine.

 

My car is a 2000. I haven't had any software updates that I can remember. Maybe a few years ago under warranty, but I don't remember anything recently. Are there some known software issues that could cause this?

 

Volvo comes up with updates quite a bit that help out with problems you will never know about.

I would check the coils first.

 

May be the problem is from electronic accelarator. If you have Cruise control you can check the problem in that way. Turn Cruise on at a high speed and memorise that speed. Go much slower and then put Cruise to catch your memorised speed. If your car accelarates well and fast then the problem is from electronic accelarator. Else you have problem with your machine, maybe the injectors, problem with petrol filter, or the quality of your petrol. Here in Athens we have a pattend that deactivates the electronic accelarator and make the car to accelarate much better. I put this pattend (which is very easy to be installed) to my previous car VW Passat 2001 and I din't believe in my eyes. I am going to put it at my new Volvo V50 but not now.

Teo. Athens, Greece