1997 vw jetta is bucking after driving 20-30 min. keeps going, just keeps bucking . Also, the speedometer dosen’t always work.
If a transmission and speedometer misbehave at the same time, I’d look at the vehicle speed sensor (VSS) first.
What’s the routine scheduled maintenance status? Check engine light on?
also check the distributor cap. My 97 Jetta the rear clip sometimes comes loose and that can cause the whole engine to buck as it misfires.
Could also be a cracked ignition coil that misfires when hot.
You may have two problems. The speedometer problem is probably related to the vehicle speed sensor, or the wiring to it. Does the engine only have problems when the speedometer doesn’t work?
Does the bucking happen constantly, or only under load? Or is it only at slow speed? That would help determine if its ignition (and what part) or transmission problems.