Car bucking under acceleration

[robbie19]

I have a 91 Z34 5 Speed. Sometimes under hard acceleration (usually 3rd gear when merging) the car with buck violently and the rpm's will drop and come back up (they dont drop all the way to zero). It almost feels like I'm braking and releasing again and again but with the rpms going crazy. I also seem to have lost top end power according to the butt dyno.

My plugs, wires, coil packs and ignition module all have under 20K on them. They are aftermarket OEM.

Anyone have any ideas what this could be?..I was told the wires could be bad.

Thanks,
Rob

_________________

14.949 @ 91.69 MPH

[grandprixgtp_91]

could be your crankshaft position sensor. my car did the same thing and it was the wire running from the crank sensor to the icm. also could be timing, but if you havent fooled with it , then its probably not that.

Jake