poopie boy

okay so this is whats going on.. this almost always happens on streets or congested freeways.. going 5 to 25 miles per hour.
its at 1500 when i have my foot on the gas, then i let go and it gradually comes down to 1200.. at this point, if i hit the gas, the tachometer will drop down to 700.
how will it go down if im hitting the gas?
sometimes its like at 1800 and it'll go down to 1400 then up to 2200 then back to 1800 just jumping around.. it happens when my foot is on the gas or when its off, i don't switch during this it does it all by itself.
then today i drove home from work and when i turned it on it went to about 700 or 600 like normal, so i hit the gas and then come to a stop and it goes to just over 300, and the whole time home, even while driving 90mph i couldn't get it to go past 1000.
the car is driving fine, it sounds great, i don't feel it struggling and its performing like a v6, just the tachometer goes crazy.
what could it be?

2DMax

iTrader: (2)

Is the tach driven by a cable, anyone? Maybe the cable is worn.

Flava_24/7

iTrader: (46)

That happened to me. The tach would just geek out. Some time it wouldflip all the way past redline and sit there.
It eventually quit working all together.
Ive spoken to others who have had the same issue. They just crap out eventually.