My 1985 TPI has very intermittent spark on Cylinder 1 only at idle but strong sparking above 1200rpm / 25* advance. It only appears to be #1 missing at idle.

The new Haltech ECU controls the cranking advance and the ignition (advance) map, and the onLine readings when the engine is running are exactly where they should be.

The primary and secondary coil ohm test is in range and so is the magnetic pick up coil.
A new flame thrower 7-pin ignition module has just been installed.
Ground is good and 14volt power is steady.
New plugs and wires.

Any tips on what testing may help diagnose problem in preference to just randomly replacing every component $$$$$

 

Swap the plug wire with another one, does the problem stay or follow the wire?

I'd also be looking at the condition of the cap and rotor.

 

Good tips,
I agree that’s a good place to start as it appears to be in the distribution of the high voltage (rotor, cap and wires) rather than on the low voltage side.
Is it possible the magnetic pickup is not working at low RPM but happy at higher speed, or does this coil either work or not work?

 

I agree with Komet's suggestion


It's incredibly unlikely that the p/u would create an issue that would only show a symptom in one cylinder. All the p/u coil does is generate a signal that says, "NOW, NOW, NOW, NOW, NOW...."

Any symptom that is isolated to only one cylinder, is highly likely caused by something in the cap, wires or plug for the affected cylinder.