Thrillho

I don't really have a traditional GAB installed, just drilled some holes of varying sizes in the top of the filter holder and also using a K&N drop in filter, but is it possible for a GAB or a CAI or any other sort of aftermarket intake to throw a code? Perhaps the airbox or maf is getting more air than it's intended to, and confuses it for a leak, and thus forcing things to run more lean than it should? I have a "small leak" code that's undetectable by most OBDII scanners, mine doesn't pick it up, but more expensive OBDII scanners pick it up. Could this be because of the GAB?

Donkeypunch

drilling holes in the air muffler isn't going to throw codes

Thrillho

Really? Damn it. I'm just so cautious with this car now because despite how powerful it is already, I think nissan went out of their way to prevent any simple modding with the way they programmed the ecu to throw codes left right and center whenever the smallest thing is adjusted.

I've no idea where the leak could be coming from. Checked all the hoses and connections. I still gotta figure out the evap and fuel systems, maybe everything will be wavy gravy once I do something over there.

DennisMik

iTrader: (2)

What is the code? Check the flexible coupling between the MAF and the throttle body that it hasn't cracked.

But the term small leak is used with codes for the evaporative system (pollution controls).

Thrillho

Don't remember the code, it could've been either P1440 or a 41.. And I know it's the evap system, but this car is a bit of a puzzle because a lot of the time when you fix something not related to the code, the code clears and/or the performance returns.

The flexible coupling is torn a little but only where the metal band sits, it doesn't go beyond that.

DennisMik

iTrader: (2)

If you have the P1448 code in addition to the P1440 code, fix the P1448 code first and the P1440 code may go away.

The P1440 code is a pisser to troubleshoot without the factory tester. as it has 20 or so possible causes. However, one of the most common causes of this code is the gas cap. The valve inside the gas cap goes bad or the o-ring is bad. I am assuming you tighten the cap until it clicks.

The air box has nothing to do with this.

Thrillho

I don't have the 48 code, it's either 40 or 41. The gas cap is a possible culprit but my gas tank hisses when I open it to fill it, so the o ring has to be good since it keeps in the gases. As far as the valve inside the gas cap goes, that I don't know. I didn't even know there was a valve there. And yeah, I crank that cap until it clicks 6 times or so.

DennisMik

iTrader: (2)

The valve inside the gas cap slowly lets air into the tank. You will only get the hiss when you remove the cap right after shutting off the engine. If you remove the cap after the car has been off for several hours, you won't get the hiss.

P1440 is EVAP System Small Leak, P1441 is Vacuum Cut Valve Bypass Valve.

The bad news is that if you get the hiss, the gas cap is probably good. You could still try one, but I don't think it will help.

Here is the list of possibilities from the service manual for P1440:

Possible Cause
Incorrect fuel tank vacuum relief valve
Incorrect fuel filler cap used
Fuel filler cap remains open or fails to close.
Foreign matter caught in fuel filler cap.
Leak is in line between intake manifold and EVAP canister purge volume control solenoid valve.
Foreign matter caught in EVAP canister vent control valve.
EVAP canister or fuel tank leaks
EVAP purge line (pipe and rubber tube) leaks
EVAP purge line rubber tube bent.
Blocked or bent rubber tube to EVAP control system pressure sensor
Loose or disconnected rubber tube
EVAP canister vent control valve and the circuit
EVAP canister purge volume control solenoid valve
Absolute pressure sensor
Fuel tank temperature sensor
O-ring of EVAP canister vent control valve is missing or damaged.
Water separator
EVAP canister is saturated with water.
Fuel level sensor and the circuit
EVAP control system pressure sensor
Refueling control valve
ORVR system leaks

Here is a link to the 2001 service manual. It is probably the same for all years of the 5th gen. Go to page 531.

http://boredmder.com/FSMs/Nissan/Maxima/2001/EC.pdf

Thrillho

It's the P1440 one, but I think the fuel system can be eliminated since I run 94 or at the very least 91 and have ran so much seafoam and royal purple and gumout and whatever else in the gas tank that the fuel system is sparkling clean right now.. I'll go take it apart tomorrow and see if I can find an actual leak, otherwise I'm going to need to read about the evap system and how it works.