QANTAS has been plagued with more engine problems, with one of its planes carrying 234 passengers to Melbourne forced to turn back to Perth.

The flight crew noticed the problem between five to 10 minutes after QF768 took off from Perth at 2.50pm (WST).

"Soon after take-off, the flight crew detected some vibration in the left-hand engine of the Boeing 767 aircraft," Qantas spokesman Simon Rushton told AAP.