Where is the air filter located on a nissan sentra 1996

Question edited for clarity.

See the diagrams

https://www.google.com/search?q=location+for+the+fuel+pump+relay+nissan+Sentra+1996

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Black soot coming from the exhaust would be excessive fuel.
The list includes injectors, fuel pressure regulator, fouled plugs, faulty coil, dirty air filter, and so on.

did you replace it with new one, or used one?? also have you replaced your air filter and used NISSAN only air filter. something tells me that you had non nissan/aftermarket air filter installed and that is why your air flow meter failed. you need to use nissan air filter ONLY in your model nissan. sentras do not like non nissan air filter, because non nissan filters are not coated in small amount of oil and let foreign particals / dirt go pass the filter and that will fry your $500 air flow meter.

common fault in this vehicle is air flow meter and temp sensor, if temp sensor fault normally will blow black smoke at the tail pie, air flow meter will have symptoms as you described.

A tune up consists of the followig: -Spark plug replacement -Air filter cleaning/replacement -Fuel Filter replacement -Engine timing correction.
So yes, you must do a tune up every once in a while and a must before an emissions evaluation. It's not very costly and can be easily affordable by someone who can purchase gas for everyday use. For a 1996 Nissan Sentra, most of the cost will come from the spark plug that you will buy and the labor cost for correcting the timing of the vehicle.

Disconnect the air ducting between the air filter box and the throttle. Clean your throttle body interior with a cloth and plenty of carb choke spray (WD40 is good too). Idling is controlled by the engine's computer and the Idle Air Control Valve IACV . This device allows air passed the closed throttle plate when the engine is at idle. Locate the inlet port in front of the throttle plate in the inside wall of the throttle body. Locate the IACV on the outside of the throttle and remove it. Give it and associated passageways a really good clean. Make sure the valve and valve seat are free of crud. Re-assemble and this should cure the problem

The cabin air filter on this vehicle should be located behind the glovebox.You will need to remove the glovebox to get to the access panel for the cabin air filter.Pull the cover off which usually consists of a few clips.Slide the filter out and you are ready to reinstall.

Should only take about 15 minutes to change the cabin air filter. Nissan did in fact provide a location behind the glove box. Remove the glove box by releasing the two pins at the bottom. Then using a phillips screw driver remove the black cover and this will give access to the filter slot.

lOOK BEHIND THE GLOVE COMPARTMENT. Compartmet is probabily plastic and all you have to do is push in real hard to get them past dash board.

IT IS ON THE HOSE THAT BRINGS AIR INTO THE AIR FILTER HOUSING