Xservice0183

My Nissan Maxima is driving about 14mpg. I drive very low rpms, lots of stop and go, but only 5miles (back and forth) commute most of the time. My Trans oil is probably not so great, my car does shift kinda hard into 2nd or 3rd (I don't know much about when it's shifting, but I feel it!). I rarely drive it over 3500 rpm (But OMG, my Revolution Sensor is giving me an Error, How do I know if my RPM Meter is being honest), take my word for it, i'm not racing it.

I've done my homework and searched for things which may affect mileage and found out the following:
PCV Valve
Fuel Filter
Oil Filter
Air Filter
Spark Plugs
Tire Pressure

I do get 2 ECUs, 14: Speed Sensor (AKA Revolution Sensor $99 replacement), and 54: Automatic Transmission Control Unit Signal to ECU (Don't know what this is, but Autozone Rep told me to fix Code 14 first, they might be linked). I don't know if these codes should affect my mileage.

My main inquiry, is how do I check if the above items are good or bad. I can see my Fuel Filter, ya it looks like it's black 3/4 but I don't know if that's outside or inside, and I definitely don't know if that's bad or good.
Tell me how to check each of these things, what is ideal tire pressure, I have some brand spankin new V-Power Spark plugs I'm going to install over the weekend.
Got a new Air Filter less than a year ago from Sears.

I would like to resolve this as quickly as possible, but i want to learn how to recognize these individual components.

Fork

iTrader: (2)

Until you resolve those two ECU codes (14 & 54), others will not appear. I think the ECU displays codes in priority. I've only seen a max of 2 codes from my ECU, yet I've had other problems that didn't appear until I've solved the first two.

For example, I had code for a stuck evap canistor valve and a ignition coil. When I cleaned up the coils and the evap, I then saw an O2 sensor. Now it's all good.

So, get those two fixed, then other codes might follow. Crappy fuel is usually Knock Sensor. Do a forum search - poor fuel economy or crappy fuel econ ...

kbmaxima

iTrader: (11)

I've done my homework and searched for things which may affect mileage and found out the following:
PCV Valve
Fuel Filter
Oil Filter
Air Filter
Spark Plugs
Tire Pressure


My main inquiry, is how do I check if the above items are good or bad.[/QUOTE]

just change all of them with oem parts. it's not much money anyway. nothing FRAM, sparkplugs must be NGK copper/plat whatever your taste. and u can buy a tire pressure meter at any autoparts store for a couple bucks.

Wetballoon

Ideal tire pressure, open the center console and look for the sticker. I think that's where it is, otherwise, look at the door jamb.