Engine surges on deceleration

[maldotcom2]

If i'm cruising at 80 or above and lift my foot, the engine will surge as the rev's come down. I can see the needle jumping around on the tacho and hear the exhaust warbling. It disappears as soon as i touch the accelerator.

Any ideas?

[Chirpstr]

At what revs does it mainly jump around? Mine use to jump around say, from 1700rpm -1500rpm. It was the transmission torque converter not functioning correctly at those revs while decelerating with your foot completely off coasting...

[delcowizzid]

how olds the O2 sensor they can cause that sometimes if they arnt switching fast enough

[maldotcom2]

Well, if i accelerate and it drops to 3rd, then as i lift off it will shift to 4th then it surges. I'm using a shorter diff ratio so around 2k. The faster i'm going the louder the surging, at 120 it's pretty damn obvious. I believe torque convertor locks up in 4th so maybe it is torque convertor. The transmission is on the way out so i wouldn't be surprised.

Oxy sensors are new, but in a post a while back i said one bank was running rich, i've put the old oxy sensor back into that side but it's still sooting up the back of my car. I'll put the old one back in the other side aswell and see what happens.