When you switch the primary injectors off and secondary

injectors on - the EC2 is still providing the same pulse duration (assuming

engine manifold pressure, etc are the same) for the almost twice as large

secondary injectors as it did for the smaller primary injectors. Ergo, you

are feeding the engine almost twice the fuel (for the same engine

conditions) as you did when on the primary injectors.  The engine is choking

on too much fuel. 

 

Unless, of course, you have made the mode 6 adjustment to compensate for the difference in the flow rates – or will mode 6 not handle such a big differential.

 

Al G