BlackCloud83

ok my 02' 6.0's MAP sensor is reading 10.9 hg on my scan tool ( kinda low ) but my mechanical gauge hooked up to the intake right next to the sensor is reading a pretty steady 19hg ( very healthy ) just in spec too... this was taken with a warm engine at idle.. is my misfire being caused by this ? any way i can test the map sensor with a multimeter before buying one new?

i think i may have found the true culprit of my lean sparkplugs and p0300 random miss ( pcm is misreading actual conditions and putting fuel in for the wrong conditions )

joecar

Your mechanical gauge is a vacuum gauge, it measures vacuum relative to BARO.

The MAP sensor measures absolute pressure (relative to absolute zero/void).

Vacuum is related to MAP as follows: VAC = BARO - MAP


BARO is appox 29.9 inHg at sea level
Your MAP is 10.9 inHg
VAC = 29.9 - 10.9 = 19 inHg which matches your vacuum gauge reading.


Or, if you prefer psi:
BARO = 14.7 psi
MAP = 5.4 psi
VAC = 14.7 - 5.4 = 9.3 psi = 19 inHg


Or, in Metric kPa:
BARP = 101 kPa
MAP = 37 kPa
VAC = 101 - 37 = 64 kPa = 9.3 psi = 19 inHg

joecar

To test MAP sensor:

with scantool connected and showing MAP sensor, apply vacuum to MAP sensor directly (using handheld vacuum pump)...

for every 2 inHg on the vacuum pump's gauge, the scantool should show a 2 inHg drop on the MAP sensor...

i.e. if pump shows 10 inHg vacuum, then MAP should show 10 inHg less than BARO.

BlackCloud83

hey thanks alot ! i never knew about the conversion, map sensor is fine !

joecar

Cool