Flat spot on full throttle acceleration

[bny82]

My sister's 1992 liberty 2.2 auto na does this crazy flat spotting when you give it full throttle acceleration from a stand still its like very rythmic it does it 3 to 5 times and then clears up and will go up to redline no probs.
If you take of with up to 75% throttle and then jump on it 100% its fine.
If you give it full throttle while driving it shifts back and goes to redline as if nothing is wrong.
This problem is on upon take off it goes up to about 2000 rpm and drops to about 400rpm and goes to stall then come alive to 2000rpm again then drops to 400rpm again does it about 3 to 5 times then all is well again and back to normal operation.
There is some old codes for knock and o2 sensor.
Grrrr to this car!

[stipro]

It sounds like a TPS issue to me, I would check that first. Have you tryed resetting the ecu??

[bny82]

Cool thanks yeah I have reset the ecu still the same. i'll get right onto the tps.
I hate this car and it hates me both mum and dad's liberty's are good to me but not my sis's lol.

[BXSS]

Not sure if its comparable to your problem, but my Impreza would sort of buck @ closed loop RPMs (up to 3700 on that car), then run perfectly in open loop (3700rpms+) up when the O2 sensor was bad.

That car ran super-lean with a bad 02 sensor.