I´m having trouble with a Fiesta 1.4i cat cvh 1991 with  EEC-IV.

Runs smooth on the road at higher speeds, fuel consumption is high and
engine is lazy especially at low engine rpm.

But the big problem is driveability at lower speeds, when stopping at the
lights the engine dies for a split second when letting go of the
accelerator. The car jumps lika kangaroo and is very nasty to drive in the
city because of this.

But, after having disconnected one battery lead, so the ECU "forgets" what
it has learned, and connecting it again, the car runs just fine for a day or
two. No jumping, runs smooth, good power at low rpm:s. So it seems the ECU
learns bad habits after a few runs.

I have a LED in the dash monitoring the output of the oxygen sensor (HEGO,
it turns on at about 0.4V), mostly it blinks like it should but sometimes it
just is on for a hundred kilometers or more. So there is some instability in
the system, but where?

Have changed the ECU, MAP, HEGO, EDIS, TPS, PIP, Ignition coils.

Have measured the output from the TPS, ECS, ATS, MAP, VSS continuosly during
driving and they are OK, no intermittent failure there.

The engine should be in a fairly good shape otherwise, it´s been driven
120.000km and the valve oil seals are also changed so oil consumption is
nearly zero. No air leaks in any air hose or exhaust pipe before the HEGO.

One thing I haven´t checked yet is the fuel pressure and the regulator on
the "carb". Guess the fault must have to do with these things.

Or, any suggestions? Or is it best they come and take me away, to the funny
farm..

TIA,

Magnus