Agreed, without a scope this will be difficult to solve.

But perhaps, this could be looked at another way... ignore the ICU for the time being and assume that its good.

If so, then which of the remaining components that have not been renewed cause a problem such as this?

- Cold start valve, leaking fuel?

- EHA?

- Throttle position sensor?

I could replace these, as they are substantially cheaper than a new ignition control unit or a KE Jetronic CU. But could either the cold start valve or EHA, if malfunctioning, truly cause the symptoms described?

If not, then the only things remaining that could cause such symptoms would be either of the control units.. or an intake manifold vacuum leak.

Everything else has been tested and found to be functional: coils, plugs, distributor caps, rotors, fuel injectors, idle air hoses, oxygen sensor, plug wires... the valves were inspected during injector renewal and were found to be remarkablely free of deposits; by extrapolation, I assume that the fuel distributor is clean as well. Duty cycle is within range and no fault codes are present.

Any input as to whether a cold start valve or EHA renewal is warranted at this point?