Ian, any chance you have a funky tune programmed into the AFC that is kicking the maf into nutso mode?

 

Car runs fine with the A32 MAF and JWT ECU from Broadaiga.


Wiring

Stephen - first - thanks for taking the time to help.

I re-checked the wiring a 7th or 8th time with schuss after testing the MAF. I had him independently go through it with his car parked right next to mine. Then again with both of us just to make sure. We tested the voltages on his car and paired them up with the Tomei connector. Exactly correct.

So the wiring simply is not the issue. 4 people have now verified with me that it isn't, and we checked against a 300zx parked right next to it. I can't check it any more thurough than that. Not sure what to do.

I used this diagram to wire it. I then compared the diagram with schuss' 300zx by testing the voltages with a Craftsman Voltmeter.

Tested on my car with key in ACC key position:
A= No Pin
B= .43 Volts (AFC also read this reading as .43-.45 in ACC)
C= -12v
D= -12V
E= +12v
F= No Pin

Then tested schuss' car the same way:
A= No Pin
B= .45 Volts
C= -12v
D= -12V
E= +12v
F= No Pin

Fuel Pressure

I am at 40PSI of FP. I always have been since I put in the Walbro FP. I believe Broadiga's ECU he sent me also is "Stock FP" and it runs just fine. (except lean up top).

I'm not sure now if I need to lower it to 32 and if I do - I'm not sure how to lower it without spending $200.00 I don't have right now on an adjustable FPR. Except that I DO have a Cartech FMU sitting aorund. It won't drop FP at idle however.

Do I need to lower it or not? Does the fact that Brodaiga's ECU works fine tell me I don't need to?

Vaccum
Delio -
I was at 5 vacuum because my BOV wasn't plugged in and the hose to it was the problem. (intake leak) I am at 19Hg vacuum now. Still doesn't explain 3.7 volts at the MAF I don't think.

If anyone else can think of any ideas, I'd love to entertain them.

 

Delio - No - no correction is set on the AFC under 39% throttle. or under 4000RPM for that matter.

So at idle, it does absolutely nothing.

 

You should not be getting -12V at the two ground pins (C and D), unless you had the positive lead of your voltmeter on the ground pin of the maf and the negative lead on a 12V supply, such as the positive terminal of your battery.

Backprobing the pins on my harness connector with the ignition on but engine off, I get the following (I just now went out to my car and took the measurements):



Turning the engine on gave me 1.1V at the signal pin B with the engine idling.

 

I was testing the grounds by putting the + lead on the E (+12v) and then using the - lead on the brown and black wires (C,D). If it's a ground, it hsould give me -12v when the other lead is on a +12V source.

How did you test it? My car is outside and I can go test during my lunch break.

Where do you have your brown wire (C) going to? I just put mine on an engine bolt...that's what the Tomei directions say to do as far as I can tell by the diagrams. The Black wire (D) goes to the black wire from the stock MAF harness.

 

Okay, that explains why you got -12V.

I tested by backprobing with the positive lead and with the negative lead on the negative terminal of the battery.

I am running the extra ground wire to the engine, like you're doing.

So you're getting .43V from the signal wire with key on, engine off, but it immediately jumps up to 3.7V when you turn on the engine, and at idle? Just making sure I understand correctly.

 

And nobody's been fooling with the decel settings of the SAFC?

 

i know what you mean iansw. when things dont go right there are so many ways to turn it gets confusing. it looks like your problem is in the
fuel delivery but if you look at jay and the guys the only thing they have over you is fuel control. so once you get that settled bam!! 400hp. good luck.

 

Exactly what's heppening. However - on the 300zx, it reads around 1.4-1.6 volts at idle. And runs great. So that eliminates the MAF being bad as a possiblity.

So wiring is good, Z32 MAF is good, FP is at 40 - but like you said - FP shouldn't affect MAF voltage.

I haven't touched even 1 setting on the AFC. The decel is turned off completely.

 

My guess after rereading this AWESOME informative thread is that everything has been eliminated, except that the JWT ECU isn't programmed for a Z32 MAF.

It runs fine with a A32 MAF, but not a Z32 MAF, and the Z32 MAF checks out fine, so it *HAS* to be the JWT ECU, right?

 

The fact that there is a 3.7V maf signal at idle is the problem. This is going to be a problem for any ecu, so I don't think we can point a finger at the ecu yet. We have to figure out where this signal is coming from and correct it. We know the maf itself is good because it works fine in schuss' 300ZX. The harness connector wiring has been checked out. What other possibilities are there?

1. Has the Tomei harness been inspected for cracked insulation on any of its wires leading to the oem maf harness? Maybe there's a little voltage from the 12V wire leaking into the signal wire. But that would happen with the ignition on engine off, too, it seems.

2. Electromagnetic interference? The maf harness should be shielded, but I don't think the Tomei harness is (not sure, though). Ian, try wrapping the harness with aluminum foil, or you can get some copper shielding tape made by 3M (it's expensive, though, $25 a roll).

3. Gremlins. Call an exorcist.

4. ???

 

Nono - I ran the A32 MAf with the "Z32 Program" and it ran like crud too.

It runs with the A32 chip and A32 MAF like it always has - but no configuraiton with the new chip works.

Wait........I'm going to go check the wiring right now again........<going outside>


I'm back!

Well son of a.....

Just checked - it is wired backwards. I swear I checked it a bunch of times.

Maybe someone snuck out to my car and switched it on me this morning.

white wire is reading +12v, black with stripe is reading .27. White wire is plugged into the red on the stock harness, not the white/green like it should be.

I feel like such a tard for even posting this after being so adamant about it.

Damn...I suck.

 

Hah! I knew it. I was going to list that at the top of my suggestion list above but I didn't want to p*** you off.

Well, I'm glad you got to the bottom of this.

 

Here's why I think the MAF voltage is so high on the Z32 MAF:

Since the element is seeing LESS air flow due to the larger cross-sectional area of the Z32 MAF at idle, the ECU is compensating with more current to heat the element to X-degrees. However, I'm betting there is more to it then this, like a scaling difference due to different hot wire elements between the A32 and Z32.

Any of this hold water?

 

Well son of a b!tch, you figured it out while I was reading my FSM and posting.

Glad you got it figured out.

 

Well, I still have to put the Z32 EEPROM in and the Z32 MAF back on (right nnow the harness is tapped into the stock A32 Harness, so i was able to test that way).....but yeah - this I'm sure is it.

I won't have time tonight because I have to go out to dinner with the wife - but I'll check tomorrow after work.

IanS

 

Just curious, but what kind of connections are you using for "taps" and is that your permanent solution or just temporary?

 

Well, maybe this thread will help others in the future. Some moderator should take all the info listed here and seperate it out into a sticky.

 

Would, if I could.

 

!#@$*(!&@#%(*!&%!@#$(!*@&$!@(#$&@!#$!!!!!!!

IT WAS BACKWARDS!!!!!

$#!@%@!#$*&!$@#%(*!&@%*(&!!!!!

Wow...we suck! I was checking that wiring with you too.....SUCK!

S

 

yes, they're pretty permanent. They tap into the wire without disturbing too much the original wire then it just clips closed. Pretty hard heat-resistant plastic too. (Not that I'd use it on a manifold or anything - but works fine over by the MAF)



You can buy them, and all sort of other connectors way cheap - Here

 

I was afraid you'd say that. IMO...the MAF sensor is pretty critical and I'd sodder/heat shrink it, but I know that's a pain in the azz.

At least on the 5th gen, I'm sure it's the same though, as I posted above the ECU is monitoring the resistance of the MAF hot wire by current flow, which IIRC is V=IR. So, those little crimp on 3M scoche connectors have to reduce the amount of strands being connected, ie raising resistance, which lowers the current. May be negligible, but it *COULD* cause some kind of side-effect.

Also, I'd be concerned about using those if any wires are shielded, as StephenMax suggested above.

Just my .02, which aint worth jack~!

 

Well, you have good points there. It doesn't look like the wires are shielded at all from what I can see.

But I will get them soldered ASAP.

 

On my 97 and on another 98 they are shielded. It's more for EMI than anything like Stephen said. The shielding is grounded on 1 side and "open" on the other.

I went through it when I found out all 3 wires to my MAF were bad.

 

OK - I had some time today to get back to it after work.

Switched the leads around, put in the Z32 MAf, put in the Z32 EEPROM, and started her up.
1.0-1.2v at idle

So I let it idle for a little bit. At first it sounded like it was running somewhat rich, but after a few minutes, everything evened out and it sounded fine.

So I checked for a CEL - yep - I got some.

0402 - Fuel Tank Temperature Sensor
1005 - EGRC Solenoid valve <---I've always had this with the JWT.
1008 - EVAP canister purge volume control valve
1302 - MAP/BARO SW Solenoid/Valve

So anyway - I figure "ah - it's a casualty of the 96 EEPROM in the 95 ECU - I'll take it for a drive."

So I start her up, pull out of the driveway and head down the road. Keeping her under 2000RPM for the first mile. I heard one small backfire. I hear those often, but usually when engine braking on the freeway due to my 3" exhaust.
"So it's a little bit rich...hmmm" I think.

I get to a long straightaway and do some mild boosting to about 4500RPM.

2000RPM - feels good.
2500RPM - feels better.
3000-4000RPM - Car bogs hard at me. Almost like you get when you have your SC piping comes loose after the MAF and you are trying to run it.
4500RPM - feels fine again.

So I do another run, watching the voltage reading on the AFC. Same thing happens, but voltage seems to rise linearly as I go. Doesn't spike/drop or anything. MAF seems to be good.
Do it again, watching FP and EGT's - they look normal too.
So it looks like something with the vacuum system goes phooey (EGR?) at these RPMs. (It feels JUST like a major vacuum leak). Could also be a misfire, but it just didn't quite feel like that.

I inspected all my piping, the SC belt, etc...all looks tight and happy. Checked for leaks around the MAF too - the gasket appears to be holding up. (it should, it's brand new...)

So it looks like it's probably the ECU now. 96 EEPROM w/95 ECU just doesn't work right.
I'll be calling JWT next month when I have the money and getting that done for my 95 ECU.

I'm out more money of course, but I learned a few things...

Edit: Vacuum also looks great - 19Hg at idle. Exactly what it always is. Boost looks to be steady when the hesitation happens also. No irregularities with the vacuum/boost gauge anywhere.

 

What's your fuel pressure doing?

 

Ian...

Your issue is a casualty of having the MAF on the charged side. I had the EXACT same problem. I don't know what StephenMax did to combat the problem. Because I would love to move my MAF back to the charged side.

As soon as I moved it over to the NON charged side. These issues went away, others cropped up though. But again, I don't have my recirc setup yet either. So that could be my fault.

 

Well, would have been nice if someone mentioned that before.....hahahaha.

FP is 40 at idle, 52-55 and rising steady at 3000-4000RPM.

So StephenMax is a freak incident?

Come on Stephen - tell us your secret!!!

 

I had mentioned it previously... I'll go find the link

 

http://forums.maxima.org/showthread.php?t=237574

Post #10

 

Serendipity.

To be honest, I didn't know there was any driveability issues with putting it on the charged side, I thought it was purely a maf survival issue. I sure haven't been having any driveability problems since relocating to the charged side.

 

Stephen this is what I stated in your thread that I linked above, back in August of last year.

"I took a gamble and put it on the pressurized side and the car would buck heavily at 0 vacuum and not go into boost well. As soon as I moved it over to the non-pressurized side that problem went away. "

How it works for you is beyond me. I know I pm'd you about it. Still wondering if there is something special your doing.