It's Impossible 2

[Terry Martin]

Tuck wrote:
> 
> Switching out the fuel pump accomplished exactly zilch.  Same problem as
> before - stumbling at high rpm's (starting at, and randomly above 3800 rpm
> - which is where the secondary injectors switch on).

Having zero hands on with the vehicle is a significant impediment. The
number of variables must be reduced to even approach the problem. 

One is to isolate the secondary injectors from the electrical system,
ie, by using some big switching transistors and power them straight off
the battery.

Does it get progressively worse above 3800 or stay the same?

Usually the shortest distance between an intermittent problem and the
answer is to identify what is not the problem. 

BTW, changing the fuel pump does not address the issue of delivery line
restriction, particulary if the pump is sucking from the tank, (as
opposed to pushing from within). It can easily draw vacuum gaps into the
line, which cuts the fuel delivery when they hit the pump. An air leak
on the pick-up side of the pump does effectively the same thing.

T