I have a fuel economy problem with my car. Everyone has claimed that maxima's should get at least 18mpg on city right? I tried searching around the forum for help but no help. I was asked to change the sparkplugs, fuel filter, but it still doesn't work. What I am getting right now is around 10mpg no matter how easy I take it on my car. The last time I did a tuneup was around 40000 miles and it is now at 93000 miles. The only thing I did was actually changing the spark plugs to the bosch crap. If anyone can help me to fix this 10mpg crap. I would really appreciated it. Especially when gas these days are so expensive.

 

I would say get another good tune-up. Air filter, fuel filter, spark plugs (put ngk in there, not bosch), check the O2 sensors, engine coolant temperature sensor, little things that all add up. That's what I did and my car runs excelent. Also, clean your throttle body and check for any CEL's.

 

why not add a little fuel injector cleaner while your at it, doubt it will help the MPG issue, but its good practice to do for a tune up.

 

Also over-inflation of tires (not excessively) contributes to better fuel economy, handling and tread wear.

 

The Bosch plugs are your problem. The german plugs dont do well with the Maxima. Go with a NGK double platinum ($12 each) Yes they are expensive but being that you dont maintain your car religiously, go with that. They are stock.

 

I use Denso Iridium plugs and my car runs flawlessly. I'm on 35,000 miles on the same plugs now.

I was a big proponent of 89 octane fuel. I tried 91 (super) once because it was on sale Super Tuesdays... and I got better fuel economy.

I get about 19mpg city and 25 highway. The most I have driven a tank on the highway is 400 miles and 300 in the city.

Since you are getting 10mpg my best guess is that you have a bad oxygen sensor somewhere forcing your computer to run rich.

I do not know if all the 02 sensors are the same but it might be a good idea to just buy one 02 sensor and change them sequentially. Change one. See if it improves, if not- put the original back on and change another one. Or you can just change them all.

 

Do you have any codes from the ECU? Is your CEL on? Make sure you check all your fluids and filters. Oil, p/s, brake and coolant should all be changed if they weren't touched for 60K. ALso, check your air filter, fuel filter. Treatments like seafoam could help too.

 

First off definately put the NGK plugs in the car. A new fuel filter every 30K miles is a good idea too. The second thing to take a look at is the ECTS sensor. It might be slightly out of spec. The Haynes shop manual has the resistance -vrs- temp table for you to verify it. The next thing I'd look at are the O2 sensors. Both front O2's control your air/fuel mixture and if there not transmitting the correct information back to your ECU that could cause you to run a bit rich, burning an excessive amount of fuel.

 

I recently changed the 240SX fuel filter in, so that shouldn't be a problem, then I will go and get the NGK platinums. When I get the sparkplugs, I wouldn't have to set the gap right? Also, people are talking about using a torque wrench? I don't get what it is because I tried going to lowes and asked for a torque wrench and they were like what the hell are you talking about? The next thing is that if the O2 sensors go bad, shouldnt it throw a CEL code? Because on my car it has no CEL codes, or is it a hidden code which I would have to use a scanner to find out? I'd appreciate all of your help.

 

Lowes or home depot wouldn't sell torque wrenches. Maybe pep-boys. I know that my autos teacher orders his directly from snap-on.

 

Not always. I didn't get a CEL and two of my O2 sensors were bad when i had my car looked at for another problem. Buy a Haynes manual and find out how to test all the parts, best $15 I've spent.

 

Improper torque on your spark plugs would not result in lower MPG.

Dont listen to idiots.

And idiots: This guy is here asking for help. If you want a brainstorming session go talk in front of the mirror. Dont make someone look for a torque wrench when it will not solve anything

 

I had that problem, I changed the spark plugs to Iridium (NGK of course), feul filter and oil... Topped up on gass and was still getting the same milage. I then cleaned my air filter (have a K&N) and after that I got my milage back.. definatly air filter will also make a huge difference...

 

Also forgot to mention, if you do all the other "tune up" stuff, it still wont matter too much if she is breathing like she has asthma...

 

I run NGK Iridiums IX plugs...work great, check you O2 sensors....fuel filter....I ran Bosch Platinum +4 before and they seemed to run fine, but I've heard not so good stories from other people though.

 

What I am trying to make sure right now is that if the 02 sensors would bring a CEL light or not? If its suppose to and I am not getting a CEL light, that means there is nothing wrong with the O2 sensor right?

 

bad O2 sensors would not necessarily cause the CEL light to go on. Another thing is the temperature sensor. if the temp sensor stays on cold the computer will make the car run rich.

Its a toss up. But its your car

 

Check your ECU for stored codes. The only time that my MPG went anywhere near that low it was when I had a bad KS. A bad KS by itself will not trigger the CEL.

Other things to consider are low tire pressure and dragging brakes (this issues alone will not drop you MPG's that low, but comnbined with other issues they will certainly not help). Both of which I had at one point or another, and fixing them helped my MPG's.