Hello,

"When running above idle speeds, the injectors will stop pulsing for anywhere from an instant for up to 10 seconds. I determined this by backprobing an LED into the injector wiring and seeing the LED stop flashing every time the engine cut out"

I'm confused by the above statement. If the injectors have stop pulsing for 10 seconds meaning no fuel injected into the engine for 10 seconds, the engine must have surely died. No engine can stay running after 10 seconds of not any injector firing fuel. Unless of course the car is on the move.

Are you rigging this test in a moving car? Of course there will be fuel cut out when slowing down or running down hill. And the ECU knows this by feedback from the TPS, CPS, AFM and rear axle sensors. So it cuts fuel. Otherwise the engine RPM wouldn't go down. Otherwise fuel will be wasted during running down hill.

I think you may have placed undue interpretation on this 'noid light' LED test. It's supposed to be a simple test where the LED is connected to the injector electrical socket to indicate whether the injector is receiving electrical impulse or not (i.e firing or not). Its for 'no start' condition where this 'noid light' test would point the problem elsewhere e.g. faulty ignition system or fuel pump. I don't think this test is appropriate to map the injector running pattern.

If your engine is running well at idle but cuts out outside idle (even when throttle is held steady) then something else is missing. I think even slight reduction in throttle would reduce the airflow which reduces engine RPM. This split second reduction in rotation is sensed by the CPS (via the 60 plus 'holes' in the tone ring on flywheel) and ECU cuts the fuel. This event is also 'seen' by the AFM which measures the change in the platinum wire's resistance due to reduced airflow. Maybe this is what you've seen by those momentary 'missing pulses' from the LED. I may be wrong as you know how steady you've held the throttle.

Anyways I've read that in Porsche's 944 the injectors are wired to two grounding terminals at the ECU (but these terminals are connected together inside). This is to reduce the electrical load on the terminals. Our ECU have only one grounding terminal (that's pin18) for all the injectors. Check its connection.

Load test the ECU terminal electrical connector (for pin18) by inserting something that's 0.04 inch wide (a needle maybe). It should grip the item strongly. I'm not sure whether this applies to our cars but its a free check. You could have a loose connector. Load test also other connectors in the ECU electrical plug. Injector plugs too.

Regards,
Amarin.