I replaced the KS, reset the ECU drove around for a week... Car feels a little more responsive but still seems to be lacking full power, and worst of all I just got 19mpg (mostly Highway!!) on the last tank... not good... Changing KS did not bring my MPG back up and I now have no codes... 0505... everytime I check

I am going to check the obvious things (as soon as I get time) but does any one have any idea?
what could be screwed up but not giving code?
sound like anything someone else has dealt with (I know theres someone!)

Like I said.. I am gonna check spark plugs and clean my air filter and change the fuel filter (still can't get the damn hose off!!!)
I plan on cleaning TB and IACV and EGR when I get the time...

I seriously doubt the spark plugs are bad cause they are fairly new, air filter isn't that dirty and would not cuase this big a problem even if it was. Yes, I checked air pressure... I don't know about the others either... I just want my MAX back!!

 

O2 sensors affect MPG a lot...

 

 

Don't O2 sensors usually give a code when they go bad?
Eh I have't replaced it... god knows I have replaced everything else on this car so why not this...
I swear if I ever find the guy who owned this car before me I am gonna run him over...
So any other suggestions?

 

 

Replace that fuel filter. Shoot the ends of the hoses with pb blaster and try to twist the hoses first. PB works great to loosen rubber items.

Dave

 

When they go bad, yes.
But when the signal is there but incorrect the ECU will see the sensors as working. It can't realize that the information it's getting is indeed a bit off. Remember, the front O2's determine a/f ratios. If thats off, your MPG will go south. Power at WOT shouldn't be an issue, even with bad O2's. Normal driving is where you'll see bad O2's have an effect.

 

Nearly 100% of my exhaust system has converted to rust. My grounding strap is disintegrated. I have new front O2 sensors installed, but my mileage did not change.

Do you think the grounding strap could be causing them to read screwy and lose mpg?

Dave

 

lol I feel the same way with my car. The more I tinker with stuff the more I notice shotty wiring, gobs of silicone sealer, things left unplugged. It's ridiculous!

 

dude that is the longest thumb i have ever seen.....

 

Thats a great question!

The harness for the o2's have a seperate ground wire for the sensors.
That puts them at the same ground level as the ECU.

 

There is no ground wire for the o2 sensors. Two heater wires and one signal wire.

 

well... I am gonna go get some PB blaster and try that. Change the Fuel filter, check/replace spark plugs... If this doesn't help I will see about testing the O2 sensors. And check grounding...
and... who knows.. maybe I just got a bad tank of gas...wouldn't be the first time... Gas stations in Houston are questionable... we'll see in about a week

anyway

 

on the O2 sensor(s)... I'm getting about .123472340 mpg with a dead knock sensor and dead O2 sensor.

 

I do know the front sensors are just 3 wires, so if that's true then the grounding strap on the y-pipe is an important part of the circuit. It makes sense - the heater def would require 2 dedicated wires, and of course with signal that leaves...nothing.

Tonight I investigated that and found discontinuity from the sensor body to the frame ground of the car. After installing a new grounding strap, it restored continuity.

I'll find out in a couple of days if it's made a difference in mileage - I sure hope so.

Dave

 

What grounding strap? I have no such strap on my aftermarket y-pipe and my o2's operate correctly. If anything, the o2's are grounded to the motor via the y-pipe and exhaust manifolds.

 

Thinking back, it is actually attached to the catalytic converter very close to the y-pipe.

And while it _should_ be grounded through the studs into the manifold, I'd guess they put the strap there in case rust ruins the conductivity of the connection. Like I said, my y-pipe was ungrounded for whatever reason.

Dave

 

Well that just suckz... Then grounding issues can occur with rusted exhaust systems.

 

Hello there. New to this site, but have some suggestions about removing the fuel filter. I have a 98 SE that I recently replaced the filter, but getting it out of there was a real PITA. The biggest reason is that the top of most replacement filters is plastic while the bottom is metal. Once the plastic gets heated from the engine over time, it basically "bonds" to the rubber fuel line. I found that by tracing the top line to the nearest junction (underneath the TB) you can disconnect that line and leave the line to the top of the filter on until you remove the entire filter from the car. Then, you can either try to remove the bottom line while reaching from the top of the engine bay or jack up the car and drop the filter down and remove it that way. Much easier that spending half the day waiting for PB Blaster or WD40 to soak into it. Much less cussing as well!!!

Good luck to you -- sorry, but don't have any suggestions concerning the mileage.

 

That's a good idea.

However, I should make it clear that PB Blaster lubricates rubber hoses/tubes/exhaust hangers in a matter of seconds. Just get it wet, and use a pliers to twist on the rubber. It will work in there very quickly.

Dave

 

replace ur 02's...and since u want to regain that HP make sure ur not reusing ur airfilter..

 

cool. I will try PB Blaster, and if that doesn't work (it better!!) I will do what Tfvesquire said.

I just wish I had time to actually work on my car... school is killing me...

 

Hi Dave:

I agree that PB Blaster is fast (my "all day" comment strictly related to this post), but because the plastic end of the filter is pointing upwards, it is nearly impossible to spray the end of the upper hose and let it soak in because it points down towards the ground. Even if you sprayed it from below the car, there is enough of the plastic end inside the fuel hose, that will not get "lubricated." The lower fuel line is normally not a problem because that end is metal. The top fitting is the problem. I still don't know why they make the filter this way. If both filter ends were metal, replacing it would be simple. In addition, you don't want to soak the fuel hose too much and then put a pair of pliers on it to twist it off. Depending on how old the hose is, you could end up with a leak. Best of luck to the 3d Man and whoever else is planning on replacing their filter and thanks Dave for your info.

 

You keep mentioning plastic filter ends... all OEM filters are full metal construction.... so I'm not sure what brand filters you are talking about.

 

Like Nirav said, I too have all-metal Nissan fuel filters. I can see how plastic would be much more difficult.

Dave

 

I am referring to aftermarket, replacement filters such as Fram or Purolator. When I went to replace the filter on my car recently, it had a parts store filter with the plastic top line. I went back in through the work orders on the car and the prior owner had a mechanic install the filter approximately 50K miles before. I tried to get an OE filter, but the day I was going to do the replacement, the dealer didn't have one in stock. The reason for my post is that I'm sure there are many Maxima owners, including myself, that have vehicles with a store bought filter installed that they will have to remove whether they choose to replace it with a similar unit or OE. A store bought, quality filter that worked for more than 50K miles in my opinion is just as good as the OE one and definitely cheaper. Just hope this post helps someone who may run into the same problem I did.

 

Finally Changed the fuel filter today... what a bastard... finally just had to cut the fuel line at the end of the filter to get it off
and after all that!! the filter wasn't even that dirty! fuel coming from outlet was clear and fuel coming out from inlet side was kinda darker... like weak iced tea...
anyway... I guess that wasn;t my problem...
I am going to move on to the rest of the stuff this weekend.
I did notice one thing today that I have never noticed before.
When i had the engine running I was looking down at the new filter to make sure it wasn;t leaking and while my ear was right next to it I noticed a very faint clicking noise from the TB area... very regular. click click click... every second non stop
any idea what that could be? As far as I could tell it goes away when I throttle it a little, but maybe the engine was just too loud to hear...
IACV? (<- I don't know exactly how it works...)