I have an interesting problem with my car that I recently purchased...
the thing is the tach jumps all around while under normal driving conditions noting in the engine changes just the tach the engine is not over or under revving but tach is all over the place.... be aware that this only happens in d4 (4 speed auto) in d3 this is not a problem or not as bad so I am baffled as to what the cause of this could be any help would be appreciated..

Thanks in advance

 

check your coil,tach feeds off the coil on a v6