Help! Auto trans won't change up--Intermittent

[kiwiPhil]

My 1991 has an intermittent problem,the auto trans sometimes wont change above 2nd unless i accelerate hard,and other times it changes just fine,any ideas before i start to spend some money?

 

[kiwiPhil]

All good now

Had the transmissiom serviced and the throttle to transmission cable correctly adjusted and shes all good now.