My 1998 Volvo S70 was running fine. But the check engine light came up with throttle error. It was re-set without doing anything and was fine for 3K miles.

When the throttle error light came on again, my wonderful but non-Volvo mechanic tried replacing the throttle sensor (about $80-100 part). The error light still came on, so they put back the old throttle sensor. But now the car is stuck in 1st gear.

They think it needs a new (used) engine computer, that the throttle part of the computer is bad.

Any other things we should be looking for? I'm a single mother and really need the car to run but don't want to blow extra $ if I don't have to. Thank you!