Hesitation when accelerating

[Dave]

I have recently bought a bravo 1.6 sx. I have found a problem when I accelerate from medium to low revs. In second gear at around 3,000 rpm I put my foot flat to floor and instead on accelerating on smoothly, the engine hesitates and then accelerates normally. This is a very irritating problem, so I will be very grateful for any suggestions to what is at fault. (I suspect the fuel injection system.)

 

[Brian]

he si t ation

Does it happen with the engine cold? My Seicento used to suffer seriously with a flat spot about 2000 miles before the service was due. New oil always cured it. Never was sure what exactly was happening.
If it's all the time, it could be the lambda sensor for the cat playing up - it regulates the mixture to the optimum for the cat, but the engine management reverts to running lean when it dies. They typically lasted 30-40000 miles on the 1.1 Centos, but were cheap(ish) to replace.