Ok - copying this over to here.
One question, can you tell if the misfire is constant, intermittent, at full or partial throttle?
You say you have changed the CPS, did you get a multi meter out, check the resistance while someone turns the engine or waves a bit of steel past the sensor to check its resistance changes with the magnetic flux?
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Someone built a sportster on here a while back, from what I remember it takes the E30 rear sus and engine/drive train complete right?
All the engine wiring is pretty much identical to the E30.
Regarding the ECU, while not 100% in tune with the details of the operation of the 1.3 I can tell you this:
CPS is critical, this is unlikely to be your issue but is easily checked if you have a spare one, Where in the country are you? I have a sensor that I extended the lead on to use as a diagnostic sensor, can be fitted and the cable looped over the rocker cover in about 2 minutes.
Air flow meter is how the ECU senses load, the ECU is relying on the AFM to get the timing and fuelling right at partial load.
Air and Coolant temp sensors - these more or less act as a fuel and timing adjustment to the base map, If these are dead it will cause over or under fuelling at nearly all engine temps and loads bar full throttle.
Oxygen sensor only functions at partial load and tries to trim partial load fuelling to stoichiometric.
Throttle switch has 3 function - closed for idle control (should click as it closes) Partial throttle and full load, full load is at about 80% throttle or more.
It is a very simple TPS and is not variable, its only really on or off so either works or it doesn't.
The inductive sensor on the plug lead is there to act like a cam sensor.
The dizzy is driven directly from the camshaft so detecting the high frequency pulse done HT lead 6 tells the ECU where in the cycle the engine is.
Not sure what the ECU does with this though.
The motronic 1.3 is really bloody simple in its function, not much more than a high powered Casio calculator. That said it's simplicity does make it reliable provided the inputs and the mechanicals of the engine are ok.
