Getting po301 & c0561 codes

P0301 is a misfire on cylinder #1, usually either a bad plug, wire or coil pack.

The speed sensor is not the issue. http://engine-codes.com/p0846_chrysler.html

It sounds to me like a passing gear issue. Or even and Over Drive issue. Try this to find out. When you put the car in gear, instead of O/D, try regular drive. If you have a push button O/D then deactivate it. If you only have Drive, then try shifting into 3. Run the car up to the same speeds you were having problems with. If you don't have the issues with the higher RPM's then it is an Overdrive/Highway gear issue. If it still stutters, then it could be a fuel delivery issue. Good luck.

Could be a transmission problem or something as simple as bad spark plugs.
The engine is under the most load when RPM is low and you are trying to accelerate, such as when it upshifts.
You should have the computer checked for trouble codes and hopefully that will point you in the right direction to test.
If the spark plugs have more than 50,000 miles of wear you might start with replacing them.

no 4-3 or 3-2 downshift
uncontrolled downshifts outside range of kickdown switch
poor acceleration from stopped position
parking pawl will not engage
selector lever does not engage in r or p
engine will not start in p or n position
smoke in exhaust (fluid loss)
fluid loss between torque converter & primary pump
howling noise when changing gears (under full load)
howling noise which increases as engine rpm increases
1st gear & reverse too loud
3rd gear too loud
rattling noise at 1500 rpm in all positions except r
light grinding noise in p & n positions
rolling noises when driving in reverse
vacuum control circuit
Vacuum Control Valve (E300D & S350D)
Vacuum Amplifier (E300D & S350D)

Hello
The Engine and Automatic Transmission (not applicable to manual transmissions) in this vehicles drive train are fully electronically controlled by a computer called the PCM and TCM (Power Train Control Module, Transmission Control Module). When a problem like this or other drive-ability related problems occurs the computer stores a record of the problem (there are of course some exceptions to this, like the fuel pump, engine coolant temperature sensor and MAF sensor for instance) in the form of a fault code in its memory, to read these fault codes you must have the systems memory scanned with a special tool. Once the fault code(s) are read you then must perform the appropriate diagnostic testing to find and resolve the problem(s) DO NOT REPLACE ANY PARTS UNTIL A TRAINED TECHNICAIN HAS DIAGNOSED THE PROBLEM TO AVOID SPENDING YOUR HARD EARNED MONEY ON PARTS THAT MAY NOT CORRECT THE PROBLEM. Also always check fuel pressure for correct spec for your make and engine type.

SORRY,tranny trble,gonna have to replace, get 2nd opinion please!!!

have you replaced your O2 censor yet? or changed your air filter lately. I know our avenger is pretty picky we had a dirty air filter once and it seemed like the O2 censor went out because it kept trying to shut off when the idle was lower. a new air filter did a bit for it then we got a censor reader that you plug into the brain box of the car or the cigarette lighter and it told us the O2 was out and our car was doing the low idle thing. after we fixed it no problems.

The po301 is a misfire code. The backfire can be caused by a excessive amount of fuel, bad valve timing etc.
My guess is you have damage to an exhaust valve that may have occurred when you had the timing belt problem.A compression test will indicate if you have a leaking exhaust valve.The reason for the backfire is the exhaust valve is still partially open when the spark plug fires.

try changing your fuel filter