Help!
My son has a 1997 Fiesta 1.25 Zetec. Broadly the problem is as follows;

1. At idle it revs in a cyclical manner up to about 300 revs and then down to almost nothing before ‘catching’ again and reving up to 300 revs and back again etc.
2. When driving in traffic in 1 st gear this ‘uneven idle’ manifests itself in a very uneven speed, like ‘kangaroo petrol’.
3. When changing gear, especially from 1 st to 2 nd , it takes a few seconds to ‘catch’ before the power comes in.
4. When driving along, if you ease off the accelerator to decelerate very slightly, the car seems to loose power and there is again that ‘delay’ when you press down on the accelerator before it catches again and jerks forward.
5. At idle, if you press the accelerator very slowly, nothing seems to happen at first as the accelerator moves down and then it ‘catches’ again and revs.
6. The unevenness of idle seems to pretty much disappear when you rev to about 2,000 revs.
7. This problem started (or got very considerably worse) after we disconnected the battery to work on the elctric windows and then reconnected the battery. May be a red herring, but may be relevant?

We have changed the temperature sensor , the plus and HT leads, and finally the Mass Airflow sensor. It is fine sometimes, but then the problem reappears.

Can anybody help, please??? Thanks in advance.

Edited by Very New Mechanic on 16/09/2010 at 22:00