ahhh ok, well my KS is fine, dont have any of the rpm probs, like ud get from a knock. i looked at my exhaust system, and wow, its a mess ill get pics, rust all over, its bad]

here are sum pics

 

 

You might not even know if your KS is bad...you could have bought the car with a bad one...it is a trouble spot that most I30/Maxs experience.

Of your KS fails will not experience knock or get a CEL but the code is in there when you check the ECU.

If your knock sensor fails then a sort of safe mode is activated which retards the ignition timing just to be on the safe side since the engine can no longer detect knock because the sensor is dead...effects of this are decreased HP (about 20 HP according to various dynos I have seen on here) and sh!tty gas milage. I remember when mine crapped out I was getting about 17 MPG on a city/ highway combo. After replacing my KS along with all three o2 sensors, I started getting about 23 MPG on the same city highway driving...

Two good article on KS replacement:
http://www.skippynet.com/maxima/knocksensor.htm
http://www.motorvate.ca/mvp.php/507

Also, it looks to me like you could really, really use a full aftermarket SS exhaust (y pipe, cat, b pipe, and muffler)... that **** is rusted.

 

tell that to my ****ing parents, "oo its fine replace it when it falls off, its uspposed to rust like it, all cars are like it, its fine." the ****ing o2 sensors are rusted into the pipes, the muffler hanger doesnt do anything what so ever, its broken, the flanges are peeling apart, its a ****ing mess, i need everything up to the resonator replaced, everything behind that is fine

 

Somewhere I think I mentioned that lowering the weight of your car will make it run more efficiently. One of the easiest ways of doing that is NOT to always run with as full tank. Now, I'm not recommending that you keep it near empty (because that is bad for your exhaust system). What I am saying is the following:

A gallon of gas weighs 6 pounds. The I30 has an 18.5 pound fuel tank. If you keep it a little less than half full (around 8.5 pounds), you will not be dragging around 60 pounds of dead weight needlessly.

Another suggestion I have for cars with automatics is to use the gear selector to shift instead of the gas pedal (when appropriate). You will use less gas because you will have more control over the throttle and your shifting will occur without any subsequent lag than if you just push and pray.

Lags in shifting really waste gas. I swear that my gas gauge drops every time I floor it.

On the other hand, I don't know how your car shifts, but mine tends to downshift into 2nd gear moreso than 3rd regardless of how much I push the pedal or how fast I am going.

 

Ok guys im down to a knock sensor replacement or an o2 sensor replacement, which one do u guys think is the culprit

 

I'd put my money on the O2 sensor.

 

His problem is related to maintenence issues not his method of refueling.

 

You HAVE to check the codes before you can determine if the KS is bad or not. DO that first.

 

I was referring to my own quote here.

 

OK?... good for you...

 

its the ks i bought a new one

 

I still get 25 on mine

 

If so, then why do owners spend magabucks to get a carbon fiber hood just so their car can weigh 40lbs less? The answer is that the less weight you carry, the faster your car can go, but the less gas it also uses.

I have seen road tests that show how removing 100 lbs of dead weight from a 3,000 lb. car can improve its gas mileage by as much as 7-8 percent, and after a year's worth of driving that amount can translate into a savings of $150 -- enough for a new mod.

 

This is true, but only if that weight reduction is suplimented with other weight saving measures. For example, 40 by itself does not mean anything at all. However 200, 300, or 400 does.

I doubt that. I would believe that you could maybe gain 1 MPG maybe if you were lucky. I am skeptical of any claim that asserts that one can gain almost 2 MPG by simply removing 100 lbs from the car. That is like the weight of some little kid.

The bottom line is the subxero's horrible fuel economy is not due to running more weight in his car by filling up the tank completely at refueling. It is due to maintenance issues.

 

i30ds wins the mega bux for that one lol, if anything the most noticeable difference with using gas up will be acceleration, u accelerate alot quicker with less weight, . but now i need tof ind out what else is wrong, im still riunning on my first tank since i put the new knock in, and well im at half a tank right now with 100 miles on the trip, this is also on 89 octane. im hoping that my gas gauge is wrong and i havent used up that much, we will see in due time, i have no other trouble codes in the ecu, i dunno what can be wrong

 

Now that you have replaced the KS, you need to replace some other things as well, like the 3 o2 sensors, air filter, fuel filter, and spark plugs while you are at it. They are all really easy to do. Remember you do not need a CEL to have bad o2 sensors. They are a normal wear and tear item and will wear out with enough age. I ran on sh!tty o2s for quite some time before a CEL was actually triggered.

 

I'm confused with my car's erratic behaviour. The previous week/fillup I drove mostly highway 430 miles that took 16.438 gallons which is 26.15 mpg ...

This week, I drove all city (didn't even get onto freeway) and made 166.2 miles out of 10.483 gallons which is 15.85 mpg !!!

Normally on a mix of highway/city driving i have been getting around 20-22 mpg ...

Why such a variation ?!?!?

 

Because highway driving is more efficient than city driving.

 

that's okk dude but less than 16 mpg ?!?!? i agree that EPA rating is under ideal conditions but still they rate it as 19 for our I30s right ?

I do follow many threads on O2 sensors and most of the ppl here tend to say "if ain't break, don't fix it" but you seem to say otherwise. I know my car might need new O2 sensors as I have 115k on them and it did throw CEL once for the O2 sensor a month ago but the CEL disappeared and didn't come back again.

 

well, i suppose 16 is a little low for all city driving. I get about 18-19 all city. So looks like you need a tune up. If you have 115k on original o2 sensors, I would say it is time for new ones. I know a lot of guys say if it aint broke dont fix it, but that is not the way I feel about things. An oxygen sensor does not have to be completely malfunctioning causing the ECM to throw codes in order to be less than efficient. I remember when I replaced mine, I was getting codes for only 2 of the 3 o2s, however, when I tested them using my multimeter, the 3rd one that had no code was indeed not operating with in the FSM specs. They are a normal wear and tear items and the newer they are the better they work. Those things sit in your exhaust pipes and get hit with all that heat and soot eventually they will begin to feel the effects of hit. Other things that will help are- fuel filter, air filter, and spark plugs.

 

i dont want to touch the o2's unless they need to be replaced, they are rusted into the pipe u know, but ill see if it persists if it does, ill take em out look at em and decide from there i think

 

I'd suggest that if you are running stock pipes and plan on going to a performance replacement in the future, wait until you do the mods. That way, sticking new o2 sensors on new pipes will be an easy thing to do.

 

chances are i wont do that until my pipe falls off at this point, i wish i had the money to do it all right now, as much as id want to, it would be nice to feel the extra pony's, but alas i wont be able to yet, is it easy to go up to the manifold to take the sensor out, any advice?

 

I dont understand. The sensors sit in the y pipe not the manifold. All you need is an o2 sensor socket to remove it and then disconnect it on the other end in the engine bay. After that, follow the wire and break the plastic tabs on the wire that secure it to various points.

 

i dont have a sesnor remover lol, but its up there i mean, the sensor is rightoff the mani on the pipe

 

You need a o2 socket because of the wires.

 

ahh thanx for the heads up