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MAP Sensor Testing

ryxj

NAXJA Forum User
Location
Westminster, CO
I tested my MAP sensor last night and I'm not sure I did it correctly because during the test the XJ ran terribly! And now after the test it seems to be running better!

I've got a '95, 4.0 HO, AX15 that is running really rich. I replaced the o2 sensor a couple of months ago and just got around to testing the MAP.

What I did (following the Haynes manual):
- Disconnected the electrical connector from the MAP.
- Jumped pins A and C from the electrical connector back to the MAP pins (A back to A, C back to C).
- Put my voltmeter on pin B of the MAP.
- Turned the ignition to ON, but didn’t start the engine.
- Got a reading of 3.5
- Then I turned the engine ON and it ran like crap! Sputtering, stuttering and the exhaust smelled even worse than before!
- Got readings of 1.5 to 0.9 as it warmed up and as I revved the engine.
- Turned off the engine and put it all back together.

After the test I pulled the codes and got a 12 and 14 - both about the MAP sensor. Unfortunately I didn’t pull codes before the test! D’oh! So I don’t know if the test caused the codes or if the codes were there before the test!

So, did I do the test it correctly? Is it supposed to run like crap during the test?

I plan on resetting the codes, drive it for a bit, pull the codes first, re-test the MAP, and then pull codes again… But I want to make sure I’m testing it correctly!
 
Some folks say putting a lower temp thermostat in can cause a rich condition. Has it been changed. I think 195* is what you need.
 
Turfzilla said:
Some folks say putting a lower temp thermostat in can cause a rich condition. Has it been changed. I think 195* is what you need.

Its got a 195* t-stat in it. I just replaced the whole cooling system in August. (CSF 3 row radiator, water pump, t-stat, hoses, heater control vavle...)
 
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