Car chugs and jerks like crazy while cruising

code p 0720 refers to output shaft speed sensor (OSS)---circuit malfunction===causes ---wiring --- OSS sensor--- ECM---TCM
as the OSS reports shaft speeds to the TCM so that he correct ratio can be selected, I would be having it tested / replaced

Plug it in for sure.. Clear the computer first off. Take the sensor off and take WD-40 and spay it in the hole that the sensor covers.. There could be a build up between the sensor and the cam, OR you could have a crank sensor problem, check that after you clear the computer and clean the hole.

That should still be under a warranty!

Acceleration problem - is it so tough? - Car Forums and Automotive ...

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Once I reach wanted cruising speed of 35 mph or above (and the car ... At that point I keep pressing pedal slowly but car does not accelerate or needs eternity to speed ...Fuel pressure within specs (40 psi in idle) and fuel pressure regulator holds ... "The 3100 V-6 engine is mated to a 4T60E four-speed automatic overdrive ...

Could be speed sensor.

The first thing that needs to be done here is to have the engine control module scanned for fault codes, based on the results then move on.

What speed are you going when it chugs?
It could be as simple as a bad spark plug or a spark plug wire/boot grounding out.
When spark plug boots get old, the rubber cracks and lets voltage arc out the side and to the engine instead of through the plug.
This will be most noticeable when trying to maintain a speed of over 40 mph, or under mild acceleration.
The reason for being noticeable at this speed/acceleration level is that the transmission torque converter will be locked, transferring the vibration from any engine miss straight through to the wheels.

Cleaning the map sensor may seem to help but with what you are describing, it is the map sensor.

Try replacing the speed sensor on the transaxle.

sounds like you need a tune up or a coil is bad

try a rebuild kit for your carb, you have trash inside it. I had the same problem with my blazer and that fixed the problem.