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It is a manafold air pressure sensor. Pretty much it just measures how much vacume your engine is pulling. The computer uses this information to adjust fuel and spark.
 

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Ok there should be 3 wires 1 ground 1 5volt 1 return signal. (at least on the older ones) If you run a multimeter from a body ground and return signal you should see fluctuating voltage from 5 volts on down with engine running and hitting the throttle a little.

I am not sure if the pinout is the same on the newer tucks but the middle pin is the return signal on the older ones.
 

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how can you tell if it bad
hey now a shout from out west.want to know conditions before
you fixed it. I'm having rough accl. & idle. ('89 4.3 TBI) feels like running out of gas.Fuel filter, ign mod, cap rotor, usual stuff?
Any help appreciated
 

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Check all your vacuum lines. Look carefuly. I had onr going to the map that was split right where it hooks to the sensor but could not see it until I bent the hose over.
 

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SILENCE! I KILL U!
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if you blip the trottle real quick from idle, the engine will bog down, this happens the most when the vac line going to it is clogged or cut open. using a volt meter should give you some answers.
 

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Throttle position sensor, perhaps? (You can test them with a voltmeter.)

Also, are you getting a Check Engine Light (CEL)? Or have you tried to pull the diagnostic codes yet?
 

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I have a 0-3 4.3L eng and am having problem with MAP sensor voltage on volts test eng. running volts should go up when eng. is revved but mine volts go down.what gives
 

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This is why I changd back ver to a carburetor,,just too many issues with all these electronics.....forever failing and causing poor drivability issues,,,
 

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