i have a 1990 cutlass ciera 3.3 , my problem is my speedometer works periodically than stops working for longer periods. A freind told me it might be a speed sensor? not sure but if this the problem where is this located or if it could be anything else? any help would be appreciated...

Welcome to AF!!

The speed sensor is on the transmission.

Is thier anything else on the speedo cluster that doesnt work ?
If so then your ICP could be going bad due to a loose connection or broken solder joint.

good luck