So I'm pretty sure that the mechanic has been messing with my fuel injector limiter. He's looked at it three times now every time getting worse I'm wondering if I should reset this needle to its factory position myself. Would that be difficult? I'm very upset with my mechanic. Anyone know a good mechanic around Westbrook Connecticut?
Your mechanic should not be messing with the injector limiter. This is set at the factory and typically needs no adjustment. I think your engine has issues elsewhere, and messing with the injection control shaft has only complicated matters because now you have to wonder what other variables he has introduced to the troubleshooting soup.
Perhaps it would be helpful to know how the governor works generally on the 1GM10 and how the injection limiter factors into that.
The injection fuel pump has a "rack," which is like a slider/throttle that allows more or less flow of fuel depending on how far it is slid in the open direction. The position of this fuel rack depends on opposing spring pressures. On the one hand, there is a throttle spring that wants to open the fuel rack, while the governor spring opposes that and wants to close the rack.
The governor, for its part, provides the spring pressure that closes the rack as follows. When the engine starts and spins up, two weights fly outward through centrifugal force. These weights in turn are linked to a collar (called a "governor sleeve") that shoves forward against a yoke lever (called "governor lever 1"). This yoke lever has a spring on a shaft that keeps the yoke against the sliding collar. When this yoke presses forward as a result of collar pushing against it, the rotation of the shaft in turn moves the rack in the closed direction, limiting fuel.
When the engine is off and the throttle is in neutral, the injector pump rack is actually all the way opened and therefore prepared to output maximum fuel. However, in neutral there is also very little throttle spring pressure holding that rack opened. Of course, very little spring pressure is needed to do so because there is not much pressure countering it. When the engine starts and begins its rotation, the governor kicks in and opposes this small amount of throttle spring pressure that is holding the rack open with a relatively larger amount of spring pressure from the governor via the engine rotation. The net result is that the rack slides in the closed direction to reduce the amount of fuel and lessen the engine speed.
When the throttle lever (i.e., in your cockpit or whatever) is slid forward, this tightens the throttle spring which opens the rack, giving the injector more fuel. But as the injector gets more fuel, the engine runs faster, which throws the governor weights out more because of the increased centrifugal force, which adds to the spring pressure on the part of the governor that slides the fuel rack in the direction of less fuel. It is the balancing act or stasis between the spring pressure increasing the fuel (via the throttle spring) vs. the yoke pressure decreasing the amount of fuel (via the governor yoke) that maintains a particular rpm.
The injector control shaft adjustment puts a hard limit on the travel of the rack, such that it can only open so far and thus only deliver so much fuel. Screwing out the injector control shaft increases the range of travel on the rack, thus allowing more fuel on the top end, while screwing it in restricts the range of travel, limiting the maximum amount of fuel the injector pump can provide.
Also, if the throttle spring should be weak for whatever reason (e.g., stretched out), then even with the injector control shaft adjusted to allow maximum rack travel the engine may still not be able to allow the rack to open to the extent necessary to achieve maximum rpm under load. That's because despite the adjustment of the control shaft, the throttle spring itself is too weak to overcome the force of the governor. But again, this is not the first thing I would be looking at in order to troubleshoot the case you are describing.
