Possible reasons for floating speed in an automatic transmission:
Transmission problems:
* Low pressure in the automatic transmission due to a faulty pump, clogged filter or leaks
* Problems with the transmission control module (TCM) or solenoids
* Worn or faulty friction discs
* Faulty torque converter
Engine problems:
* Malfunctions in the fuel supply system, such as clogged injectors or a faulty fuel pump
* Ignition system problems such as faulty spark plugs or coils
* Malfunctions in the engine management system, such as a faulty mass air flow (MAF) sensor or crankshaft position (CKP) sensor
*Low compression in cylinders
Electronics problems:
* Faulty Vehicle Speed Sensor (VSS)
*Faulty Throttle Position Sensor (TPS)
* Faulty wiring or connectors
Other possible reasons:
* Poor fuel quality
* Worn or clogged air damper
*Faulty Transmission Fluid Temperature Sensor (TFTS)
Diagnostics and repair:
* Diagnostics with trouble code scanner to identify possible transmission or engine fault codes
* Checking the level and condition of the transmission fluid
* Physical inspection of transmission components for leaks or damage
* Checking the pressure in the automatic transmission and checking the performance of the solenoids
* Checking the serviceability of sensors responsible for the operation of the engine and transmission
* If necessary, replace faulty components or repair the transmission