Problem solved:

I tried all the methods that were mentioned in this thread (cleaning the throttle body and adjusting the cable), but they didn't eliminate the problem.

Today I took the car down to Volkspower in Burwood for a computer diagnostic test and 2 errors were found
1. Throttle position sensor
2. Air mass/Air flow sensor

They pinned down these errors to the temp switch green D plug ($50 part) and it eliminated the problem. The car was then put on the diagnostic again and all the errors were cleared.