I have this information in the Newbie section, but I am guessing that the real experts don't look much there. I'm not a newbie to much when it comes to cars, and I know that most of the forums I have delt with in the past have more info than any dealership and I hope someone will have the answer.

Here is a breakdown of the problem with a few additions.

I have had this problem since we bought the car about 2 years ago or so. The code is always the same (except a new one for the trans output speed sensor). It exibits the problems of a car running lean, slight stumble when cold, slight knocking under slight load sometimes, all the usual suspects.

I have checked for vacuum leaks, operation of the PCV system, The MAF voltage, and a few other items I thought it could be.

I have searched for MANY hours and every thread that had this problem was either a dead end (the OP never followed up), or the CEL came back on even when replacing the MAF and having the computer "reprogramed" at the stealership. In those cases the "fix" lasted a max of 6 months.

Here is some of the info I got in my MAF testing.

Here are the results:

Between ground (black wire) and Signal (White) these are the readings
I got using a Fluke 112 meter.

Key on Engine off: 1.092V
Idle: 1.426V
2.5K rpm: 2.322V
4K rpm. 3.062V
The max voltage I could get out of the meter at no load is 3.692V

The test method I used for getting the max reading was to use the max hold feature on the meter and reved the engine to almost 5.5K peak.

I know that typically a MAF meter measures the amount of air coming into the engine in Kilograms per unit of time. I also have seen that reving an unloaded engine and reading the MAF is less than the the loaded value, like actually driving the car or having it on a dyno. I know on my SC I would never hit near 5V just reving the engine, but on the dyno it would show 5V (actually it would peg the meter at about 3700).

I know that one of the guys in the thread on the how to check the MAF had 4V at 4K, I also had different wire colors as well (My car has Red Grey instead of Red Green).

Also when we first got the car the CEL would come on usually while just getting the car going from a stop around 20-30 mph driving like any normal 30 something with kids would do. The engine rarely goes to 3K and is driven by my Wife primarily. The output is linear at anything near part throttle so I am a little stumped why it's giving this code. I have used an Accuratron code reader and it will monitor several items and one of them was the O2 sensors and they were fine.


Here is the info I got from the Accutron meter I used yesterday.

O2 sensors were not ready yet, but the heater tested OK.

DTC that caused the freeze frame P0171
RPM 1637
Speed 44 mph
Load Value 35.2%
Temp 188F

Short term fuel trim #1= 8.5%
Long term fuel trim #1= 33.5%

Short term fuel trim #2= 8.5%
Long term fuel trim #2= 33.5%

Short term fuel trim #3= -100.6 %
Long term fuel trim #3= -100.6%

Short term fuel trim #4= -100.6%

Fuel System 1 Closed

Fuel System 2 Closed

I guess I missed Long term fuel trim number 4

I know that the -100.6% is telling me that the computer has adjusted all it can and can no longer compensate, so it's throwing in the towel and saying fix me.

The thing that gets me is that if the MAF was intermitant it would seem that I would be able to replicate this by tapping the MAF housing with a screwdriver handle and get some kind of odd reading. I have tried this in the past, but not with my meter attached. Now I have tried it with the meter and I get no fluctuation at all. I gave the housing a good whoppin' and the reading is rock solid. (using the record function)

My Dad mentioned swapping the O2 sensors from bank 1 to bank 2, what do you guys think? They have checked find in the past, and if the sensor is dead wouldn't it show rich all the time since most of the O2 sensors I have dealt with in the past generated a voltage based on the amount of O2 in the exhaust?

I need some real help on this one please. I have less than 15 days to get this fixed and also need to have time for the system to reset.


Thanks

Jeff

 

Hello Jeff, I have had the same issue couple of weeks ago, ended up with a new MAF. I couldn't rev the car over 4-5k RPM and MPG went from bad to worse (safe mode w/ SES on).

In addition, my Long Term Fuel Trim was the same as you, 33.5%.

Hope it helps.
PS. Which generation is that max?

 

It's an 01'. I can rev it to the moon if I wanted to but I was just holding 5.5K for the test. The car accelerates just fine and runs great at WOT with no problems. I don't think the 33.5% is too far off that's only like a third of the adjustment but the -100.6% is a problem. Based on the MAF voltages I have I don't know if it is bad or not. Like I said before an engine without a load will not move the same amount of air of a loaded engine. So barring taping my meter to the windshield I think I am out of ideas.

The Data freeze happened at only 1636 rpm at a low load and 44 mph, which by the info I got from the how to check a MAF I am well within spec at that level.

Mileage is around 20/25 city/ highway

Thanks

Jeff

 

Jeff, I'm no "expert", but I can copy/paste with the best of 'em

Hope this comes in handy, it's from the Mitchell repair program I have access to:

SELF-DIAGNOSTICS -2001 Nissan Maxima SE
Malfunction is detected when mixture ratio compensation amount is too large (mixture is too lean or too rich).
Possible causes are:
Intake air leaks.
Defective front HO2S.
Defective injectors.
Exhaust leaks.
Fuel pressure incorrect.
Lack of fuel.
Defective MAF sensor.

To set DTC, start engine and warm to normal operating temperature. Turn ignition off and wait at least 10
seconds. Disconnect MAF sensor harness connector located near air cleaner. Start engine and let it idle for at
least 5 seconds. Turn ignition off and reconnect MAF sensor harness connector. Select MODE 7 and ensure
DTC PO100 is set. Select MODE 4 and erase first trip DTC. Start engine and let it idle for at least 10 minutes.
Select MODE 7. If first trip DTC is detected, go to PROCEDUm. If engine does not start, fuel injection
system has a malfunction. Attempt to start engine while depressing accelerator pedal. If engine starts, go to
PROCEDUm. If engine still does not start, check for intake or exhaust leak.

1. Start engine and let it idle. Check for exhaust air leaks before three-way catalyst. Check for intake air
leaks after MAF sensor. If any leaks are detected, repair or replace as required and retest system. If no
leaks are detected, go to next step.

2. Turn ignition off. Disconnect ECM harness connector. See Fig. 3. Disconnect appropriate front HO2S
harness connectors. See Fig;. 12 or Fig. 13 . Check continuity of White wire between right front HO2S
harness connector terminal No. 1 and ECM harness connector terminal No. 63, or between left front
H02S harness connector terminal No. 1 and ECM harness connector terminal No. 62. See Fig. 4. Also
check circuit for short to ground and short to voltage. Repair circuit as necessary and retest system. If
circuit is okay, go to next step.

3. Check fuel pressure. See BASIC DIAGNOSTIC PROCEDURES article. If fuel pressure is okay, go to
next step. If fuel pressure is not okay, check fuel pump and circuit, fuel pressure regulator, fuel lines and
fuel filter. Repair as necessary and retest system.

4. Install all removed parts and reconnect all harness connectors. Start engine and let it idle. Select MODE 1
with scan tool and read MAF signal. With engine idling, MAF should be 2-6 glsec. At 2500 RPM, MAF
should be 7-20 glsec. If MAF is as specified, go to next step. If MAF is not as specified, check MAF
circuit. See DTC PO100: MASS AIWLOW (MAF) SENSOR. Repair as necessary and retest system.

5. Start engine. Listen to injectors and ensure a clicking noise is heard from each injector. If all injectors are
operating, go to next step. If any injector is not operating, check inoperative injector and circuit. See
SYSTEM & COMPONENT TESTING article. Repair as necessary and retest system.

6. Turn ignition off. Allow engine to cool and ensure no fire hazards exist. Remove injector assembly,
keeping fuel hose and all injectors connected to injector gallery. Disconnect all ignition coil harness
connectors. Turn ignition on and monitor injectors. If injectors do not leak, go to next step. If any injector
is leaking, replace faulty injector and retest system.

7. Crank engine for about 3 seconds. Verify fuel sprays from each injector. If any injector fails to spray fuel,
replace faulty injector. If all injectors spray fuel, no problem is indicated at this time. Problem may be
intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.

The program does make it difficult to copy/paste, tho, sorry for the typo's. There were a couple of tips offered, one was a bad PCV valve (which I see you already checked for), and the other was an intake manifold leak- the ole "spray it with carb cleaner" trick.

I just wanted to throw this out real quick for ya, but let me know if I need to do some more digging, good luck,

 

Thanks I'll check it out, but how do I "select" items and where are the figures (pics referanced).

Thanks

Jeff

 

You need a Consult II to perform that procedure, see, C&C gets you nowhere

I'd try a new or used MAF.

 

im no expert but i would check my fuel filter / housing........( mine was black, clogged up and had metal fragments in the housing )

 

Not sure what C&C is, but if my MAF readings are within spec, why in the world would I try another one? It stated the problem happened at 1636 rpm and 35% load when the Code came up. At that RPM I am well within the range in the how to for the MAF.

This would make sense, but wouldn't it be easier to check fuel pressure? Is there any way to check fuel pressure on these cars? I am guessing I would need an adapter to go to my fuel pressure gauge I already have. Seems a little short sighted on Nissans part to not include a valve to connect to and not even have a real fuel filter, but I digress.

Also If there was a fuel pressure problem, I would be knocking like a coffee can full of pennys if that were the case. And with such a high compression ratio I would expect it to under hard WOT acceleration. Am I missing something?

Jeff

 

Woops I mean cut & paste, so C&P.

My MAF readings were in spec, it's just how it goes, intermittent problems. I still replaced it and have yet to notice the same symptoms as before.

Seems as if you're dwelling on the readings a bit too hard there. Find a used MAF for cheap, www.car-part.com, and call it a day.

 

Well the Long term fuel trims wouldn't be that far off for an intermitant problem would they? I get what you are saying, but like I have stated I have searched and searched and everyone that had this problem seems to have it happen again in a few months. That's buying a new one from Nissan, having it reprogramed and it still came back.

You are the first to say that you replaced yours and all was well. How long ago did your happen? Not doubting you just that I have been on this site for over a year and though I haven't posted until the last week or so I have searched for this exact problem off and on for a long time, those that had the same problem had it to happen again.

I am going to order one, but I don't hold high hopes for a real fix.

Jeff

 

My OEM MAF lasted until 115k, and I am now @ 121k, but when it was dying, it never threw a code. Just got the intermittent death/stall, and one day on my way to work, I couldn't get passed 2.5k or so.

my STFT's & LTFT's are wacked out because of my lack of primary O2 sensors and Z33 injectors, so I can't go by that.