1993 Jetta Tachometer RPM "Surge"

Depressing the clutch while leaving your foot on the throttle causes the tach to jump every time I do it. It does this in my car, my truck and my tractor. I think there is something wrong with the clutch pedal on all 3 contraptions. It would do it on my motorcycle if I owned one. But the motorcyle does not traditionally come with a throttle pedal. Two of the three vehicles I own now don't have gas pedals either. The do have throttle pedals but they are deisels so it is hard to have a gas pedal if your vehicle does not use gas.

There is a damper on the throttle. It's a little assembly with a diaphram and an orifice that bleeds down at a designed rate to prevent the throttle from closing quickly. When you take your foot off the gas it prevents the throttle from closing instantly to reduce emissions. If the orifice is clogged it can become slow and cause what you describe. (Sometimes it's designed such that it causes what you describe even when working correctly.)

HTH.

JRE