Author Topic: Checking Map Sensor  (Read 11953 times)

Offline Tazman

  • Junior Member
  • ***
  • Posts: 774
Checking Map Sensor
« on: January 27, 2011, 07:08:42 am »
Does anyone know if the map sensor can be tested?Thanks 
Proud of and proud to be a veteran of our military.
God BLESS AMERICA

Offline bake74

  • Senior Member
  • ****
  • Posts: 5871
    • Build Thread
Re: Checking Map Sensor
« Reply #1 on: January 27, 2011, 07:33:45 am »
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
« Last Edit: January 27, 2011, 07:35:59 am by bake74 »
#1: The easiest and most obvious solution to any problem is 99% of the time correct.
#2: There is no such thing as impossible, it just takes longer.
  74 k10, 77k10    Tom

Offline Irish_Alley

  • Tim
  • Senior Member
  • ****
  • Posts: 13333
  • Family is not an important thing. It's everything.
« Last Edit: January 27, 2011, 09:39:11 am by Irish_Alley »
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline jaredts

  • Senior Member
  • ****
  • Posts: 1330
Re: Checking Map Sensor
« Reply #3 on: January 27, 2011, 11:43:45 am »
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.

Offline Tazman

  • Junior Member
  • ***
  • Posts: 774
Re: Checking Map Sensor
« Reply #4 on: January 27, 2011, 12:54:04 pm »
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
Proud of and proud to be a veteran of our military.
God BLESS AMERICA

Offline topp

  • Frequent Member
  • **
  • Posts: 498
Re: Checking Map Sensor
« Reply #5 on: January 27, 2011, 07:58:42 pm »
Fluctuate how?

Have you checked your EGR valve??
'90 Suburban TBI 350

Offline Tazman

  • Junior Member
  • ***
  • Posts: 774
Re: Checking Map Sensor
« Reply #6 on: January 27, 2011, 08:18:14 pm »
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
Proud of and proud to be a veteran of our military.
God BLESS AMERICA