I would definitely do the 100k mile tuneup and whatever else might help or gets recommended (within reason). As far as I'm concerned, there's not much to think about when you can (a) put off necessary maintenance/repairs and waste that money and more by filling your tank just to turn around and get dismal mileage, or (b) just do what is best for you, your car, and your money in the long run and do what needs be done.

For the Seafoam, as it's been said before, do it right before an oil change and do half in the brake booster line, a quarter in the crankcase and a quarter in the gas tank. My friend and I both had to get the front o2 sensors replaced within a few weeks of using the Seafoam, but it's worth it for the sake of getting all that carbon out of the system, and those o2 sensors will eventually go anyway. On top of that, the new ones will add to fuel economy.

After having done the Seafoam, some injector cleaner, oil change, new air/fuel filters, plugs, o2 sensors, optimal tire inflation/balance/alignment, and a few other fairly inexpensive things (most mentioned somewhere along this thread by others), my mileage jumped from around 19 average to around 28 average, and almost 35 when driving at 65mph on the highway. Overall a HUGE improvement and worth every bit of money and time spent.


I can't help you as far as the explanation, but I can tell you that my friend's dad used his Maxima for a few months and always used 87 despite my friend's pleas that he use 93 or at least 91, but his dad had the same attitude as that -- pish posh, 87 and 93 are the same/there's no difference/they both work exactly the same -- and a few short months later the knock sensor was mysteriously toasted.

 

The problem is that seafoam doesnt get rid of the carbon. Take out a plug, and look into the cylinder with a flashlight. you will be shocked. Not to mention killing 2 $100 sensors for a smoke show when you can add a $7 bottle of Redline SI-1 and get better results makesno sense. That is one pretty expensive smoke show.




No mystery. Knock sensors die. I would be surprised if the car was brand new. Other than that, If you drive the car, the KS will go bad. 87,91 or 93.

 

so is maxima775t wrong?

 

Has anyone gotten the combination code of knock sensor and code 0171 (lean bank)? My gas mileage has hit the crapper... about 225 miles to the tank. Normally I get 325 to 350+ miles per tank. I've cleaned the MAF a couple times with spray (first electronic cleaner and then the CRC MAF spray) and cleared the CEL, but the CEL keeps coming back and the codes are knock sensor and lean bank. Car starts fine and runs fine, just crappy mileage.

Bottom line question... would a bad knock sensor cause an 0171 code?

 

BTW - My car is a 97 with 210K miles.

Thanks in advance for your insight.

P.S. Please don't tell me to check tire pressure!

 

A bad KS definitely should not cause an 0171....

 

If you want to improve you gas mileage i learnt this trick from a nissan mechanic. I been using this method for 3 years now. A $400 job for only about $7 bottle of sea foam and $10 bottle of Lucas fuel treatment. This Job is so simple. Simply go to any auto zone or adavance and purchase a bottle of sea foam and Lucas fuel treatment. The Sea foam WILL clean your fuel injectors and ports through your vaccum line from your brake booster. You will need a slim funnel to pour the sea foam through the vaccum line slowly. make sure your tank is near empty VERY NEAR EMPTY. THIS WORKS TRUST ME. I LIVE IN FAYETTEVILLE NC AND WHEN I TRAVEL TO MY BROTHER'S HOUSE WHICH IS ABOUT 2.5 HOURS AWAY MY TANKS IS STILL ON FULL!! WOW!!!



You need:
Sea foam ($7)
Lucas fuel treatment (i suggest you buy the big bottle is about $10)

Other: I SUGGEST YOU GET A TUNE UP, NEW FUEL FILTER, clean your throttle body AND NEW AIR FILTER AS WELL. I USE K&N AIR FILTER IT'S GREAT! for maximum performance!!!

Steps
1. Disconnet your vaccum line from you brake booster. Insert the funnel into the line.
2. Start your car. you will hear a vacuum sound (sucking sound) from the line because it's sucking in air. Simply pour the sea foam into your line slowly!!! if you pour to fast the car will cut off. (then just start over and pour slowly) Pour about 1/3 of the bottle into the line. and the rest into the gas tank.
3. Cut your off for about five minutes. (sometimes the car will run when you turn off the ignition because it running off the air it will shut it self about 30 seconds or just simply clog the vacuum line with your finger on the funnel.)
4. CONNECT YOUR VACUUM LINE BACK TO THE BOOSTER. AND START YOUR CAR. leave your car running for about 20 minutes. you will experience alot of WHITE SMOKE FROM YOUR EXHAUST. BECAUSE IT BURNING ALL THE CARBON BUILT UP.
5. Cut your car off. Pour about 12oz of Lucas fuel treatment still near empty into your tank. Drive your car until the rest of the white smoke clears from your exhaust. (will still experience white smoke from exhaust while drive.) The faster you drive the faster the white smoke will clear and your fuel injectors and ports are all clean and lubed with Lucas fuel treatment. I usually drive about 60-65mph.
6. Then fill up your gas tank at your favorite gas station (i use BP gas) and fill up with 93. YOU WILL GET BETTER GAS MILEAGE!!!!!!!

 

Its not really a wrong signal. An O2 sensor operates by measuring the amount of Oxygen in the exhaust. The ECM takes the reading the O2 gets and adjust the fuel mixture with it. An old O2 can be lazy in that it changes from lean to rich but is slow doing it and may not use the full range( instead of measuring from .9-.1 volts it mainly reads about .25-.75 volts) which can have a huge effect on fuel mileage. The down stream O2 can effect fuel mileage but usually only when it has is shorted or open in either case the light will come on for it. I hope this will help you understand an O2 a little better.

 

I would think you should spend the extra couple bucks per tankful and get the 91 at least. If you " just got the car a month ago" , you haven't had time to see what's happening to the engine and how it reacts. Imop, saving a couple bucks on gas will just about pay for the sensors you have to replace later BTW here in Nova Scotia gas is about $4.00 / gal US$ - I pay $1.20CD per litre.-or more !

 

So, the two - knock sensor code and lean bank code - are unrelated? Is it likely a bad MAF that is causing the 0171? I've gotten the 0174 code (the other bank) only once out of the several times that I've cleared the CEL.

 

Correct.


Nope. Check your injectors first, then the O2 sensor for that bank.


Hmm. Fuel rail issues, maybe?

 

Thanks for the reply. I'm trying to understand which part of this elephant I should bite into first (the fuel injectors, the MAF, the O2 sensor, or who knows what)... I'm getting code P0171, the description for which is below.

How can the O2 sensor be saying that the mixture is lean AND I'm getting poor mileage? Isn't the poor mileage an indication that more fuel than necessary is being pumped in? If the injectors were plugged, wouldn't the car be running poorly because it is gas starved? If the right bank fuel injectors were plugged and therefore the O2 sensor is seeing a lean mixture, then this means the left bank is primarily doing the work, correct? Would the car be running noticeably poorly in this scenario? It's not running poorly, just poor mileage. On the other hand, if the O2 sensor is crapped out, wouldn't I be getting a code that explicitly said that the O2 sensor is bad - the 0503 a.k.a. P0130 code?

Lots of questions, I know. Cleaning the injectors is a cheap first step, but I'm just trying to think this thru before needlessly replacing parts. Thanks.

0115
Diagnostic Trouble Code 0115 indicates a problem with the fuel management system on the right cylinder bank. The right bank is also called the rear bank. It is cylinders 1,3,5.

The Front Heated Oxygen Sensor for the right bank sent signals to the Engine Control Module indicating an excessively lean fuel mixture. The ECM attempted to correct this problem by directing the fuel injectors to supply more gasoline. Further signals from the Oxygen Sensor indicate that the attempt to correct the lean mixture condition was unsuccessful, and the fuel mixture continues to be too lean.

Possible causes include ...
- Intake air leaks
- Defective Front Heated Oxygen Sensor
- Fuel injectors
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Faulty Mass Air Flow Sensor

 

An O2 sensor code only turns up when the sensor or heating element is totally dead. If it's just on the way out, the ECM can't tell.


Check the easy stuff first:

1. Listen for intake leaks (hissing)

2. Listen and feel around for exhaust leaks (putting sound, warm air)

3. Buy some starter fluid in an aerosol can and spray around all the intake tract connectors and gaskets, including around the throttle body and upper and lower manifolds, and vacuum lines. Be methodical about it and listen each time to see whether your idle changes.

4. Run a bottle of Techron through your fuel.


If you go through those steps (in that order) and can't find a problem, my money is on the O2 sensor for the bank in question.

 

i have a 98 max with 183000 miles on it. I only use 91 or 93 octane from sunoco. I get at least 22mpg with mostly driving in the city i get alot better if i don't race it or go fast on the highway
. Its not worth putting 87 in. You will burn more and that will end up costing you more money in the end. You might see the savings up front but you end up paying more in the end. I also recently changed my ks and i only use mobile 1 synthetic oil. That might be a help but the fuel you use will defintily have an effect. 87 is not the recommend fuel by nissan anyways.
Try running 91 from sunoco for about two tanks and let us know if you see any improvement

 

o2's, knock sensors, egr, coils....nissan failed to resolve these problems for this car (recall) especially coils

 

check the air filters to see if their clogged that would give u poor milage