Technical 1.4 i.e. stutters, shuts off and doesn't restart

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Technical 1.4 i.e. stutters, shuts off and doesn't restart

Yieeah

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Hi,
Following problem on an MK2 1.4 i.e. engine:
The engine starts from cold, when takes of in first gear but as soon as it gets to constant speed or decelerates, the engine stops responding and shuts off. On occasion it will restart itself and continue accelerating when the gas pedal is pumped.
Also when revved at (rough) idle, the engine stalls when the rpms fall.

Fuel filter, spark plugs, ignition coil pack and cables, hall sensor, possibly ECU have been changed. Switched lambda for fuel pump relay, no change.

Any ideas other than wiring fault or injection unit?
 
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not sure what the hall sensor is, but it sounds classically like a cam position sensor

the ECU cannot time the ignition without it, and shuts off the injectors and spark plugs
 
The engine doesn't have a cam sensor, but the crank sensor is a hall sensor.
 
The water temperature sensor (inlet manifold at the rear of the engine) is quite critical to these engines with simple ECU / EFI... you could change it or at least check the wiring is not damaged.

Also the Lambda sensor is important. An ECU diagnosis should give some clues regarding faults (but less than later ODB2 systems).
 
The heater of the lambda probe is broken, however it isn't the issue as it's now unplugged and the manual for the Monomotronic MA1.7 claims that the engine will run even with all sensors and actuators except for the ignition pack, rpm sensor and injector unplugged.

It doesn't stutter anymore either, it just turns off during driving. After cleaning every electrical connection and mass point I could find plus the inside of the ignition switch, it mostly turns off and on after shifting into third gear. If it won't turn on again, shifting into second gear will restart the engine most of the time. It does get worse the longer the car is driven to the point of not starting anymore at all. There are no cables anywhere near the shifting linkage.

The ECU error codes are lambda probe and rpm sensor short to ground, the former is unplugged, the latter new and I checked the cabling for shorts. The fuel pump is also new.

My guess is an intermittent and impossible to find contact.
 
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Why unplug the lambda sensor? It is critical to the fuelling of the car with the simple Bosch system fitted. You should fit a new sensor if the diagnostics said that it was originally faulty. The RPM sensor I think is what is known as the crank(shaft) sensor.. if this is faulty then it's a fairly regular fault for many Fiat cars, not difficult or expensive to fix.

Lambda should work without a heater, just won't work so well when cold. However I'm not completely sure if the early i.e. Tipos had a heated lambda, I think 3-wire sensors had no heater but 4-wire ones do?

Anyway a generic lambda should work fine if you wire it into the standard connectors.
 
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