Hello everyone ..
Last week I bought 2001 buick lesabre and i want to try to explain something strange .
when i start to push the Pedal and drive , the engine sound loudy . in addition when i drive on highway i allways need to push the pedal - if i release it the speed reduced very quickly .

I had few Buick'* and i know that the driving going very smoothly and quiet.
and if i release the pedal the car continue to runing . the speed reduce but slowly .

how can i resolve the problem ? i suspect in the throttle body ...

not normally any throttle body issues with this engine. you possibly have a exhaust leak, hard to tell from your description. could you post a video of the noise under the hood and slowly rev it in park to maybe 1500 to 2000 RPM

egr valve bad ??

I don't see any "service light"

How can I diagnose the problem ?
where to start ?

If would help us a lot if you could post a video of whats going on.

This is something you can not see the video.
I feel it in the car . like the car make a effort to drive . more then usually

Well, you said when you release the throttle, the car slows down quickly. We'd like to see the speedometer do this. Also, audio would be very helpful too.

If your problem is carbon buildup around the throttle body butterfly valve, the TB can be removed and cleaned pretty easily to rule that in or out. There are instructions here somewhere on the forum for removing the TB if you've never done it before. That may not help your issue but it'* something to try and won't cost you much and can only help your system overall.

For $5-6 you can buy a can of Seafoam engine treatment, and follow the instructions to run it through the engine via the air intake method. One of the vacuum lines connected to the side of the throttle body usually works well for that. That'* another method to break down carbon deposits throughout the top end of your engine.

Are you talking at highway speeds? If that is what your talking about it sounds like its not shifting into high gear and the sprague clutch isn't letting the car coast. If this is what your talking about it might be a transmission problem, but like stated above more info is needed to diagnose your problem.