let me said this.. how long have you had the battery in the car...

haha
 

brand new battery. i mean i just got it like 2 months ago. and i think that when my car does that, i mean like, when the voltometer shoots up, it might be my clutch slipping but i havent felt like the car is in neutral or not getting acceleration. o well im getting a new alternator, 70 amp, soon so that should fix the problem...but if not i guess ill have to tear apart my car to find out. well not tear apart, but just throughly check the wiring.

sometime if you have a good battery.... and it does that too... especially when you just drop down a new battery... cause it have lots of juice... and it it over charge and thats why your battery is way to high... n when you stop the accel. or step on the brake and the voltage went down or went back to normal. is because of the over charge... but thats normal tho...

well... another thing... well double check your alternater... especially the black one by itself on top of the alter.... double check that one wire and see is there any broken wired inside the tube or any cut... cause this is the problem i got on my mk2 back in the day.... those little cooper wired in the tube wired is broken and got cut... and it didnt give me good charge... and another problem i found is the bolt/nuts that have the 10mm bolt to tight down the one wired on top of the alter. is broken... i mean the black rubber siel that clamp/hold the alternater wired that tight the 10mn bolt... that rubber is broken and it short the alternater... and after i raplace this two things i ok with it.... well... sorry for the confuse... hope this help little bit...