I’ve noticed in the last day or two that my car doesn’t accelerate like it did last week. It seems that I have to push on the pedal just a bit more to get it to go. And after a few seconds of dumping gas in my engine it seems to respon. USUALLY with a body-throwback jerk. I don’t know if this is related but since this started it seems harder to slow down. I have to use a bit more force on the brake. Any ideas what that could be caused by?
Are you saying that the engine RPMs increase without it moving and after a second or two it suddenly jerks forward?
I too an unsure of the naturew of the problem but when Ms.Nics vehicle started to suffer from lack of take-off power and passing get-up-and-go we relaced the fuel filter and put some fuel injector cleaner in it and it cleared right up.
Model and age of car? Manual or automatic? Date of last tune up? It could, I suppose, be a transmission issue. That would maybe explain the jerk as it starts. And if it were failing to disengage properly, might even explain the braking issue. Not sure if there’s a failure mode where the clutch both fails to engage and disengage at the same time, though.
Need more info to even make a good guess, though. Could be lots of things.
It could be a lot of things, as you’ve already heard, but if it was my car I’d look at the accelerator pump.
Only, of course, if it was over say 25 years old and had a carb. 
Until we know year make and model, not much we can suggest.
its a '97 Chevy Lumina (sedan) and an automatic.
I don’t know if I can explain it anymore.
The engines RPMS do seem to increase (from what I can hear) before it effects the speed of the car. It also idles fairly high. After I got to 35 miles an hour, I stoped using my gas pedal and it went up to the mid 40’s all on its own. The ground was level so I know it wasn’t going downhill.
Before you spend one penny on this issue, go out to you’re car, get down on your hands and knees on the driver side, and make sure the floor mat hasn’t worked it’s way up under the pedal. What you’re describing doesn’t sound like common symptoms of this problem, but when ever I hear about problems with acceleration that’s the first thing I tell people to check. It’s free and quick. But back to your problem. Maybe a sticky throtlebody.
I suppose vacuum advance is right out the window anymore too.
Sounds like your transmission fluid is low.
My initial gut is multiple unrelated problems. Start with the accelerator cable/linkage. I think something is sticking, which would explain high idle/speed climb and increase in required braking effort to slow or stop the car. Once that is resolved, check the trans fluid level and note if it’s bright red, or brownish, and sniff it-let us know if it smells burnt.
Pretty much. 
Joey P’s sugestion is a good one. This is fairly common.
It sounds like your car is idling high which is causing the problem slowing down. In addition there may be some transmission issue complicating the issue.
Properly checking the trans fluid is a good idea. Check your owner’s manual for the procedure (it makes a difference) If low add the correct fluid to the full mark. Hint: it often does not take very much fluid to go from the add to full mark. On some transmissions it may only take a cup or so.
Do you have any warning light (check engine or transmission warning lights) on?
Update:
My father and I checked the trany fluid and it was low. I put half a quart in there and it seems to be running better. Well, it doesn’t take as much gas to get it to accelerate and it slows down a little easier. The jerks between shifting from Drive-Neutral-Reverse has gone down considerably.
So in the next few days I suppose I’m going to take it in and have em look at it.
The idling high doesnt’ seem to have gone down at all. Infact, I’ve noticed I go kickass fast in reverse. Without using the gas at all 