mtrai760

iTrader: (19)

I started out having fuel delivery issues, WAY too much fuel when starting up the car, 9.8 AFR, just bad overall. I'm running Z32 injectors and a Z32 MAF. I now believe the problem lies in the MAF wiring, though I am not sure exactly where at this point. This is related to this thread here: http://forums.maxima.org/showthread.php?t=547457

To make a long story short, I pulled all the plugs and they were all blackened from running waaayyy too rich. Replaced all the plugs, installed the Z32 MAF, and no change. Pulled the codes and got one for the MAF. Today I took the MAF down to Iansw's and put it on his car, ran perfect, no codes, so it's not the MAF. Came home, started checking wiring, and everything is wired up properly. Then I checked voltage, which may or may not tell a story, someone with experience tell me...

Going off of this picture:


I am not getting that voltage on my MAF. I get:
White signal wire - .01
Red power wire - 5.01-.02

I spliced and did not solder the Z32 adapter harness, which I know is not ideal, however I checked the readings on both sides of the taps and they are exactly the same. I plugged everything in and checked the codes again after clearing them, still the same, bad MAF. Next I wired a stock known good A32 Maf back in, and I STILL get a bad MAF code.

My conclusion is that I have a bad MAF wire somewhere on the harness, problem is, where? Has anyone run into a similiar situation? Anyone have an opinion other than what I have come up with at this point?

Suggestions, comments, concerns? Anyone know the path that the MAF wiring takes without unwrapping all the harness?

Cliffs:
Car running too rich on Z32 injectors/MAF.
Tested MAF, checked good on another car
Checked voltage at wiring - Does not match up with previously published results
Get code for bad maf, using both Z32 and A32 mafs.

Previous work done to the car leading up to this - Engine was removed, all exterior gaskets replaced, MEVI installed, engine thoroughly cleaned, re-installed. S/C installed. Problem with running rich since first startup, troubleshooting ever since.

nick

iTrader: (10)

did you check the ground on your MAF? my had a bad ground and car was runing rich and stalling. Check this thread. http://forums.maxima.org/showthread.php?t=376649

streetzlegend

iTrader: (8)

Do something, disconnect your o2 sensors the two front ones and see if its still running the same. Last week i was having same problem, at idle car was bogging n turning off cuz of too much fuel.. disconnected o2 n car runs perfect now.

Also, what are you using to tune? is it just stock ECU with z32 maf/injectors? cuz if its an safc or something similar you need to make adjustments to read the z32 maf.

mtrai760

iTrader: (19)

Thanks for the feedback, but I am 98% sure the problem is not enough power to my MAF. No AFC is hooked up or being used at this time. Just Z32 injectors and MAF, with a AEM AFPR and a Cartech FMU.

I am not getting enough power to my MAF. Reading should be approx 12v at the MAF connector power wire, which is the red or #3 wire. I only get 5v. This is causing a CEL and making the car run WAY too rich at idle. Car is a 1998, I have tried two different ECM's, both read the same voltages. Things I have checked so far-

Using the FSM
Checked voltage at the ECM, getting 11.6v at connectors 67 and 72, which supposedly supply power to the MAF, per page 282, EC-114 of the FSM.

Running a Z32 MAF and injectors. Have checked the voltage levels at the splice and the connector to the MAF, both read the same. Checked by grounding to both the harness, and the chassis, voltage does not change, stays at 5v.

Checked a known good Max, power at MAF connector was 11.8v, as it should be, key on, car not running. Checked Z32 Maf on a known good car as well, MAF is good. I am positive this is a car wiring issue, and not directly related to the MAF itself.

Per FSM, when voltage level is not correct:
"Check the following.
*Harness for open or short between mass air flow sensor and ECM
*Harness for open or short between mass air flow sensor and harness connector F36
If NG (No Good), Repair harness or connector"

So I have checked and voltage is not where it should be. I then checked the ECM, and it is putting out proper voltage. Which leads me to...

Why am I only getting 5v at the MAF connector? If it was grounding out somewhere, I shouldn't even be getting that. I have been back and forth through the FSM and I am not sure what I am missing at this point.

Anyone know what I am missing?

streetzlegend

iTrader: (8)

How about doing a test, running your own 12v from the battery or any 12v source into the maf directly. see how the car runs like that.

mtrai760

iTrader: (19)

Well I'm done. I'm a competent mechanic, but I am all out of things to check. I have:

Traced the power wire to the MAF, it also goes to the EVAP and Idle control. Either of those could have been grounding out and causing a drop in power to the MAF, but they are not. Disconnected both and I still only get 5v.

Ran a new power wire from the ECM to the MAF. I get 12v now, but still get the same issue with too much fuel and a 0100 code for a bad MAF.

Ran a new signal wire from the ECM, didn't help.

Tried 2 different MAF's, A32 and Z32, no change. Both MAF's have been tested on other cars and worked 100%.

Ran a new ground to the MAF, no go.

No matter what I do, I get a 0100 MAF and a 0105 MAP code.

I ran through the test in the FSM for the 0105 code and could find nothing wrong.

I have also tried a different ECM, no dice.

Tried clocking the MAF at a different angle, no go.


So now I am out of options. Even returning everything to stock won't fix my problem at this point. I do not know of any good mechanics in the area, but I am going to have to find one. None of the local Nissan Dealerships are worth a damn. I have run through every test by the book, there shouldn't be anything left to test, but I am obviously missing something. This is the first time I have ever been completely stumped doing automotive work. I'm probably going to get raped on diagnostic charges.

Merlyn

iTrader: (4)

I had a similar problem (wiring wise) in another car... the only thing you have not done that I did (even though it was not the reason)

swap ECM...

You have done everything but try another ECM

mtrai760

iTrader: (19)

Not true. From my post above: I have also tried a different ECM, no dice.

choray911

iTrader: (1)

What kind of fuel pressure are you running? When I first put in my 470 injectors, with no correction and the factory FPR, I threw a MAF code and the car would barely run at idol with a huge plum of black smoke coming out of the exhaust. After I turned down the pressure with an adjustable unit, and scaled back the injectors, she was gravy.

Merlyn

iTrader: (4)

ah, my bad, I thought I had read though everything and didn't see that.... sorry about that...

hmmm

The only thing I would do is rinse and repeat everything...

I had a MK3 Supra with Ignition issues, and when we finally figured everything out it was our third time around the same old tests...

mtrai760

iTrader: (19)

For fuel pressure, I tried everthing from 34psi down to 28psi. The big thing is, I get a CEL for the MAF as soon as I turn the car to the 'ON' position. I don't even have to start the car. So it is not related to my injectors.

Chris Gregg

iTrader: (59)

Any resolve? I recently endured a change in my car's running. It ran lean at idle as normal, yet would flood after trying to accelerate or boost. I found that a coupling had melted. Replaced and all fixed (except for known lean at idle).

mtrai760

iTrader: (19)

Not yet Chris, but thanks for asking. I have an appointment at a shop on Monday morning. I have to get the car towed down, since it is not driveable. Luckily, my insurance company will cover the tow through my roadside assistance coverage. I have setup a $300 limit with the shop to do their thing after speaking with the owner. He has a mechanic that specializes in electrical and has been doing it for 20 years. He said I had done all the right things so far, and with a problem like this he couldn't guarantee anything, hence the $300 limit. If they go through that and do not find anything, I'm going to have the car towed back home, and I'll deal with it once the weather improves here. At that point, I will be looking to replace some harnesses completely.

I'm keeping my fingers crossed that the shop finds something I overlooked.

mtrai760

iTrader: (19)

Car is fixed and running fine now. I'm an idiot. There, I said it.
When pulling the engine, I was marking every hose and connector, when I noticed that the connectors were all either color coded, or had a unique connector shape, so I stopped marking them.

Well, it turns out that the MAF connector, and the Absolute pressure sensor connector, are the same shape. :doh: I had them crossed. I got so hung up on the voltages being off on the MAF that I thought it had to be a wiring problem. Well, it was, self inflicted.

Car is running like a top now, clutch break-in and then I start boosting.

Thanks to everyone for the advice. I killed myself on this one.

96blkonblkse

iTrader: (18)

Haha dont feel bad man, everyone makes mistakes like that. Ive done a similar thing with my TPS. I kept throwing TPS codes, i overlooked everything, and i went out ordered a TPS from the dealer. Little did i realize that i didnt fully plug in one of the tps connectors lol.

Congrats on getting it running though!