Lionel PW 2055 engine runs fine in reverse, but barely runs forward

Did you take a toothpick or something  similar and clean the slots on the brush plate ??  Any damage to the fingers in the E unit ??

My first guess: dirty brushes, commutator, and/or brush holders.

Nothing a thorough services can't fix - best case cleaning/replacing brushes and cleaning the commutator, worst case, replacing e-unit drum & fingers.

Check the tension of your brush springs.

Engine runs again!  I did a thorough cleaning of the brush plate (communtator) and brushes.   Spring tension is good.

E-Unit was OK.

Put oil (sparingly) on the main driver axles and gears.

Also, put a bridge rectifier just before the motor to drop the voltage by 1.2 volts, thus giving more voltage to the smoke unit.    Engine smokes much better now.    (I also did this for my AF 312 engine with great results.)

Thanks for your suggestions!

Happy to hear you got your post war locomotive running correctly again. Hope you have a wonderful Thanksgiving and be sure to enjoy your train.