[rfmaster]

Gents

VSS is important as it is not only used for the lock-up torque converter control. The VSS is also used to control the EGR valve, idle speed, and air/fuel ratio. I have to emphasize that the VSS is used to control the idle speed when the vehicle is moving. Without the VSS, engine may have stalling problems under certain conditions, which in itself is dangerous. You can increase minimum idle speed with the adjusting screw and eliminate stalling, but the engine will still not run optimally without a VSS.
Somewhat erroneously many think that running "closed loop" is best for fuel mileage - it is not. In closed loop NBO sensor is being used to monitor the exhaust O2 content and ECM changes commanded AFR. There are ECM's that allow engine to run very lean (15:1 to 17:1) under certain conditions (called "highway lean mode") to improve fuel mileage during - for example steady cruise conditions (no delta TPS, no delta MAP). Without VSS, ECM will not get the correct signals to run the engine for best fuel mileage. So if you are planning to drive long distances and burn less fuel VSS is a must. For my retrofit I used JTR Part #2PRS which is two-pulse per revolution, square wave unit for all TBI installations, 7/8-18 thread, .104" square drive. BTW, I get 17.5 MPG on extended cruises (that's 6500lbs moving at 65 MPH).

//RF