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John Wood Nut Swinger
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3,413 Posts
Discussion Starter #1 (Edited)
If you run high boost and have trouble with defueling and over boost codes then you may need a map fooler. You can buy a 4.7 volt Zener, 1 watt(.5 watt will work but the 1 watt is more robust) for around $1 and install in minutes. The factory map sensor is just a pressure sensor with a 0-5 volt output that goes back to the computer. By installing the 4.7 Zener you make the computer see the same voltage as before from 0-4.7 but stick at 4.7 as your boost goes higher, thereby fooling the computer into thinking you are running normal boost and preventing it from defueling. Many folks do this the mechanical way by installing blow off valves or pressure regulators in the map sensor hose. The 4.7v Zener is just a clean, cheap, electrical way of doing the same thing. To hook it up you simpley "Y" splice the banded end of the diode to the LG/BK wire and the other end of the diode to the GY/R wire at the map sensor. It should be spliced into the two map sensor wires without touching each other and without breaking the existing circuit. Then it should be soldered and taped well to protect it from the elements.

A 4.7v Zener diode freezes the voltage at 4.7 if it goes over that, so if it still defuels due to over boost it must be either hooked up wrong or a bad diode or something strange. It should be possible to watch the voltage with either a meter with wires ran to the map sensor or with a predator programmer or other type scan tool in the computer.




Some good reading about this mod here: http://www.powerstroke.org/forum/99-03-7-3l-general-discussion/24552-did-4-7-diode-boost-fooler.html



I copy and pasted all of this info from the thread above. I want to thank Alabamafrog for his input and with tolerating my bugging him in the testing of this mod.
 
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