Nissan Repair: Burning gas like crazy, differential pressure sensor, differential switch

Question
QUESTION: Hi,

I have a 95 Nissan Altima with 96k miles on it. Recently it has been burning gas like crazy, I'm getting like 10 miles per gallon. One thing I need to mention is that my check engine light is on... are these 2 things related? Why is my car burning so much gas?

Thanks

George

ANSWER: George,

The car is in limp mode so it runs a fat preprogrammed fuel map.  I would go to autozone or checker and get the codes read for free.  After you get the codes email me back and we'll discuss a path forward.

---------- FOLLOW-UP ----------

QUESTION: Hello,

The code says:

P1400 - manifold differential pressure sensor fault

What's wrong with the car? Is that the problem causing the car to burn so much gas?

Thanks
George

ANSWER: George,

The sensor needs to be replaced.  It is on the intake and what it does is sense how much vacuum the engine is pulling.  Without the sensor working the car will consume way too much gas since the computer cannot figure out what kind of load is on the engine.  This means a pre-programmed fuel map will be used to keep from damaging the engine.  So, it fattens up the mixture to keep the engine from pinging.  Purchase a sensor and install it.  Reset the code and you should be good to go.

---------- FOLLOW-UP ----------

QUESTION: Hello,

Thank you for your help.
What is this sensor call so I can go buy it? And do you know approximately how much the sensor costs? And how do I reset the code? Can autozone reset it for me?

Thank you

George

Answer
George,

Most manufacturers call the manifold pressure differential switch a Manifold Absolute Pressure Sensor (MAP Sensor).  Autozone could sell you the part and after you install it you just take the car back and they will clear the code.  Also, after the switch is replaced just disconnect the car's battery for five minutes and that will clear the code too.