Ford Fiesta (96N) Accelerator slows engine down?

Hi,

Recently, my petrol 1.25 ford fiesta has developed an unusual fault - for the first few minutes after the car has started, the engine revs as normal (~900-1000 rpm), but if on pressing the accelerator at all, the engine revs drop very low (to ~250) and the car shakes but does not stall. The engine returns to normal speed on letting the throttle off. If I try to set off during this time the car usually shudders and stalls - if I manage to get it moving without throttle, the car will only idle along in 1st gear and stalls if I press the accelerator. After 2-3 minutes or so of idling the fault seems to disappear and the car behaves absolutely fine.

I have checked the air filter/passage for blockages and the spark plugs/oil etc are fine.

This fault seems to have become more prevelent after disconnecting the power to change the battery.

Any ideas would be much appreciated, Cheers.

Had a very similar thing with my daughter's Fiesta recently.

Advice here was to change the Coolant Temperature Sensor, which fixed the problem entirely. Another symptom I had was that it wouldn't rev past 4100 under load.

The thread is ^^ up there somewhere, entitled "'97 Fiesta 1.25 Zetec woes" dated 25/6/06.

The long and short of it is that these sensors fail regularly and cause the ECU to go into Limited Operation Strategy - limp home mode.

It's a bit awkward to get to, underneath the coil pack. If you seal the expansion tank with a polythene bag under the cap, you won't lose much coolant.

Disconnect the battery before you start (note your radio codes etc first!) to clear the ECU fault memory. Then once you've reconnected, let it idle until 2 fan cycles have happened. That took about 40 minutes! Then go for 3 or 4 miles of mixed driving. During this period the ECU is learning new settings, so it's best not to short cut the procedure.

HTH

Cheers John