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73-87 Chevy _ GMC Trucks => Fuel Systems and Drivability => Topic started by: Tazman on January 27, 2011, 07:08:42 am
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Does anyone know if the map sensor can be tested?Thanks
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The manifold absolute pressure sensor, or MAP sensor, monitors the amount of air flowing through the air intake system. When this sensor is malfunctioning or failing, you will experience excessive and frequent stalling. Your idling also may be extremely rough. When this happens, test your MAP sensor to confirm that this is the problem.
1
Check the MAP sensor for any dust or debris on the sensor. To do this, flip the sensor upside down and visually inspect the sensor wires. Make sure that the sensor wires are free of any contaminants.
2
Set the dial on the voltmeter to "Ohms" and check the resistance between the THA and E2 terminals (check your vehicle's service manuals for the exact location of these terminals on your MAP sensor). Insert one of the leads on the voltmeter into the THA terminal, and another lead into the E2 terminal. The output on the readout should be at or near 0.
3
Turn the ignition switch to the "II" position.
4
Set the dial on the voltmeter to "volts," and touch the red lead on the voltmeter to the VG terminal on the MAP sensor and black lead on the voltmeter to the E2G terminal on the MAP sensor.
5
Gently blow into the sensor's wires and check the voltage. It should fluctuate. If it does, the MAP sensor is functioning properly. If it doesn't, your MAP sensor has failed and must be replaced
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http://m.wonderhowto.com/how-to-test-and-replace-m-a-p-vacuum-sensor-circuit-251789/
Here's a site
http://autorepair.about.com/cs/troubleshooting/l/aa042603a_06.htm
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bake74: It sounds like you're describing a mass air flow sensor and not a map. A maf senses flow rate. A map measures vacuum (pressure difference from atmosphere to intake). I don't think a map has the two wires like a maf does. Sorry if I'm wrong on that.
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Thanks for the replies but it looks like that is not my issue.What my truck does is it will be idling just fine when the idle will fluctuate for a minute or so then go right back to idling fine.Or I can be driving and come to a stop and it will fluctuate.I have checked for vacuum leaks and tested or changed several items and it still comes back.Thanks
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Fluctuate how?
Have you checked your EGR valve??
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This morning when starting it idled fine for a minute or two then started fluctuating which only lasted about a minute then it idled fine again.Then stopping at a light I cut the radio and it was doing it again only slightly.Checked and cleaned the EGR valve when I replaced the intake manifold last November.Thanks