Hi wayneandlisa.
Have you still got the problmem with your Xsara? We have a 1998 1.8i and had similar problem where the thing wouldn't run at all, I could only drive it downhill and slowly, it wouldn't even climb my workshop ramps.
I had remembered the previous owner saying there was an ECU problem once and the mechanic just disconnected the battery and let it sit for a while, reconnected and away it went. I tried this, first I only left it for a coupel of minutes and no glory. The second time I disconnected it and left it alone for 1/2 hour(like a naughty kid
) and low and behold(touch wood) my wife says the car is better than it ahs been for weeks. I did also change the O2 sensor.
Good luck.
Chris (in OZ)