Questioning my MAP sensor mod?? -
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post #1 of 4 Old 03-02-2011, 03:38 PM Thread Starter
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1998 XJ Cherokee 
Join Date: Jan 2011
Location: Denver
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Questioning my MAP sensor mod??

Does anyone know what this additional sensor is? It is on a 98 XJ. It is in line with the MAP sensor and seems to be giving me problems when putting a heavy load on the engine. It just momentarily loses power and the check engine light comes on for a while. It will fix itself after removing the load and turning the truck off and back on again. I took it to a jeep mechanic and he wasn't sure what it was. Sometimes the engine will lose power when I just move the sensor. Only other mods under the hood that I know of is an ARB air compressor.


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post #2 of 4 Old 03-03-2011, 08:40 AM
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Could it be the Intake Air Temperture sensor????
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post #3 of 4 Old 03-03-2011, 01:30 PM
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2000 XJ Cherokee 
Join Date: Apr 2002
Location: out in the garage - Minneapolis
Posts: 25,794
That is some sort of MAP sensor modification to Hot Rod your Jeep. Remove it and throw it away.

The Manifold Absolute Pressure (MAP) sensor senses the air pressure inside the intake manifold. The intake manifold pressure is converted into a voltage signal that's transmitted to the engine's computer which then determines how much fuel the engine needs. Under low vacuum conditions (WOT, throttle suddenly opened) the MAP is higher, the MAP output voltage is higher, and the injectors are held open for longer to inject more fuel into the cylinders. Under high vacuum conditions (throttle closed, deceleration), the reverse applies.

The MAP sensor is basically a three-wire pressure sensitive variable resistor. The three wires are the 5.0 volt input, output voltage to ECU, and the ground wire. By increasing the input voltage you can increase the output voltage to the ECU which will increase the injector duty cycle and supply more fuel. The reverse also applies. You can fine tune your air/fuel mixture with this mod.


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post #4 of 4 Old 03-03-2011, 02:52 PM Thread Starter
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1998 XJ Cherokee 
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Location: Denver
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I definitely don't Hot Rod my jeep, just try to take it over a few cliffs here and there. Thanks for the advice, I'll get rid of it.
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air flow , electrical issue , engine , map , xj

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