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Old 04-09-2008, 08:55 PM   #1
gathermewool
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Member#: 143624
Join Date: Mar 2007
Chapter/Region: NESIC
Location: CT
Vehicle:
14 FXT Touring
VRP

Default M.A.P. sensor

Preface:

'97 LGT 180k

Obtained 5V reference voltage from the harness. Vacuum to the M.A.P. sensor is ~21 in. H2O

Haynes Manual states that the Sens voltage should vary from < 3V at idle (high vacuum) to 2V at WOT (low vacuum)

If the reference voltage is 5V and the M.A.P. sensor output voltage varies from 3-2V, I would assume the M.A.P. sensor consists of a varistor (variable resistor) operated by a diaphragm. I could be wrong, but this makes sense to me. Couldn't find anything online about the M.A.P. internals.

Question:

With a multimeter, will the resistance change with the M.A.P. sensor hooked up to a vacuum pump when measured from signal to ground. I pulled it and measured infinite resistance (open circuit) at atm pressure (vacuum pump not attached.) There was no change in resistance after applying 21 in. of vacuum (still infinite resistance.)

Varistor failure?

diaphragm failure?

dance monkey, dance?

EGR thread:

I pulled the M.A.P. sensor to trouble shoot the below listed EGR flow malfunction (P0400) problem I have. Instead of having every one read through the entire thing to answer this simple question, I decided to post it separately.

http://forums.nasioc.com/forums/show....php?t=1456396
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Old 04-09-2008, 09:49 PM   #2
munkis
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Location: brokenmotorsports.com
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Team Broken: V6 GF
rallyarmor.com

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key on if you 5v power 5v referance and a good ground at the harness with it unplugged from the sensor chances are the sensor is no good.

and yes its a variable resistor attached to a bored that is pulled on by a diaphram changing the resisitance.
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Old 04-09-2008, 10:06 PM   #3
gathermewool
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14 FXT Touring
VRP

Default

Thanks, brother. Hopefully this is the culprit. I'm not one to just throw parts at a problem. The issue now is finding a cheap, gently used MAP. $250 for a new one??? no freaking way! who's parting out!? ( checked the parting out threads ; ) )
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