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Jake
Jake, Nissan Technician
Category: Nissan
Satisfied Customers: 4023
Experience:  Experienced collision repair technician, Pulaski Tech graduate and DSM hobbyist.
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My 2007 Navara has recently dropped from about 28MPG to 20

Customer Question

My 2007 Navara has recently dropped from about 28MPG to 20 MPG. My Mechanic has plugged in his computer and can't find any faults. Any suggestions?
Submitted: 2 years ago.
Category: Nissan
Expert:  Jake replied 2 years ago.
Jake :

Hey there, generally when we see dramatic increases in fuel consumption with no fault codes. It is because of the MAF sensor starting fall out of spec.

Jake :

What you want to do is have your mechanic hook his scan tool up and look at the ALPHA readings or short term fuel trims to see whats going on. If either bank is + or - more than 5% then that indicates an issue. Depending on the amount and whether or not it's one bank or both banks will give us a good idea of whats causing it also.

JACUSTOMER-umsu058x- :

Hi Jake

Jake :

How handy are you, do you have a volt meter?

Jake :

sorry that last response was for someone else I apologize.

JACUSTOMER-umsu058x- :

I just had the jeep with my mechanic and he plugged it in. He reckoned the Mbar/Baro should have been fluctuating more than it was when revved. It only fluctuated between 1002 and 1007. Is that the reading you were looking for? He also asked me to ask you if the MAF sensor is built into the Air mass sensor. Thanks. And I'm not at all handy nor do I have a voltmeter.

Jake :

Yes, the air mass sensor your referring to s what we call the MAF in the U.S. same thing.

Jake :

and the baro readings are not what I was looking for, but if the baro readings are off then then the fuel trims are likely to be off as well because that would indicate a vacuum leak.

JACUSTOMER-umsu058x- :

My mechanic had just gotten a new computer so was struggling to find his way around it. Based on the Baro readings should I just go ahead and get a new MAF Sensor?

Jake :

No, I wouldn't replace the MAF simply off the Baro reading. Can he not view the fuel trims?

Jake :

It would be best to rule out an air leak by fuel trim readings before replacing the MAF.

JACUSTOMER-umsu058x- :

He can't seem to see the fuel trims. He had a good root around it yesterday. He did say that the MAF sensor was covered in oil so he took it off and gave it a good clean. I filled it up after that so hopefully I'll see a difference this tank.

Jake :

wow that will definately help, a dirty maf will be out of spec

Jake :

let me know please