ThaPimpShrimp

Alright so I am running out of ideas for what's wrong with my car.

All I can tell is that it's just running too rich. When I pull the plugs they're fuel soaked.


I pulled the codes for my car and here is what I got..

14 - Car/Vehicle Speed Sensor - Irrelevant
23 - Throttle Position Sensor - Tested this and it's fine, I just didn't follow the diagnostics for depressing the pedal. Wouldn't cause my problems anyway I'm pretty sure.
24 - Neutral Safety Switch - Irrelevant
34 - Knock Sensor - Irrelevant
41 - Fuel Temperature Sensor - Irrelevant


I am however getting code 31 and I am confused as to what this one means.

I've been using these web sites for the codes I am getting:
XenonZ31 ECU Diagnostics
repairs:codes [Z31.com]

So, one says "AC/Load" (No idea what that means), and in the '87-'89 model years it says the ECU is bad. I have absolutely no idea what year this ECU is from as I didn't install it.

In the meantime I am looking into that code and I seriously hope this is making sense to someone. I am clueless at this point. Just as a heads up, O2 sensor is new, CHTS is new and working, MAF is working correctly now that I cleaned the contacts and clamped it down tightly.

Also hypothetically if none of this leads anywhere, could it just be that someone who owned the car before me f*cked with the MAF adjustment screw?


Edit: So I guess the ecu has to be from an '84 model year? Also it is sounding more like 31 is just the fact that I don't have air conditioning. Well... any ideas for what I should check? I'm lost.

I dont know if this is information anyone would have, but is there perhaps a certain number of turns the MAF adjustment screw should be set at? :\ I haven't touched it and won't until I've got more info about it don't worry.


You can see a video here of what it's doing if it helps: http://www.youtube.com/watch?v=zEg--...ature=youtu.be
You'll notice partway through I was flicking that switch - it's for my fuel pump. I was just messing with things to see what affect it had.. ignore me.

NismoPick

#1: The speed sensor is what tells the ECU to perform a MAF burn off cycle. Your 130mph speed sensor needs to be swapped with the 85mph one... (I've discussed this before).
#2: How did you "test" the TPS? If it's not set / aligned properly, it would probably throw a code.
#3: Neutral safety switch... was the chassis originally an automatic? Was the ecu for an auto ( RedZ31.com: Complete Z31 ECU list )
#4: Code 31 has a dual meaning I believe. A/C compressor check, and also volt / amp system check. If the alternator is dying / dead, it may throw that code too.
#5: IS THAT A BOLT PLUGGING A VACUUM LINE ON THE INTAKE?
#6: That MAF screw is supposed to be sealed... I have no idea how to adjust it, but it should only affect idle a little bit.

So... have you load tested your alternator?
Have you checked the ecu ground wires? (I've discussed this before).
Have you checked the injector flows?
Have you checked the fuel pressure?
Have you checked for vacuum leaks?

ThaPimpShrimp

#1: I know I've heard about it. I'll look into it a bit more, wasn't there a way to manually do it? Is it really necessary or could be causing my issues?

#2: I had a friend do the test in the FSM or Haynes a while back.. I can always make an attempt to retest it. It's on my list now.

#3: Yes originally an auto, and the ECU was as well.

#4: I'll read up on testing my alternator and try that out.

#5: Errr... No! I have never seen one haha. Where do you think you're seeing it?

#6: Yeah I know it's supposed to be but mine isn't. Pulled out my MAF and apparently it's been remanufactured. Seems like it's in good condition though. I didn't mess with it and read up more. Shouldn't really be affecting the issues I am having.


#7: I did buy new clips for the ECU from a z31 but never installed them. It's a lot of work and honestly I have cleaned out my current ones and my pins on the ecu and wiggled them all around. I've seen no discernible difference. Is there a way to test if that's the problem?

#8: Have not checked in injector flows. They are supposedly only 12,000 miles old though so I was hoping that's not the case. To do so I'd have to pull off the fuel rail right?

#9: I'm buying another fuel pressure gauge tomorrow as I was wondering about that as well (friend who I was borrowing from took it back).

#10: No vacuum leaks. I've checked multiple times and can't find one anywhere(other than under my dash for climate control).

Do you have an order of attack for me on which things I should tackle first?

NismoPick

If you have an 85mph speedo (or any 280zx's in the local junk yard), just yank the sensor and swap it. Just gotta pull the cluster.

You can also do a manual MAF burn cycle by tapping into it's power wire (discussed by Afshin in the HBZ Z31T ecu/maf swap thread).

I'd start with checking the ecu grounds, maf cleanliness, fuel pressure, alternator, etc. Duowing had similar probs, so read his thread for all my suggestions: https://www.zdriver.com/forums/280zx...estions-23839/

And this is the bolt I'm asking about:

ThaPimpShrimp

Just read through that whole thread and I am doing my best to get a better grasp on what entirely this swap entails so I can fix whatever is screwed up.

You mentioned a couple times an attachment that I believe you had made regarding the z31 swap..
All of the links are broken. Do you happen to have that around still? I'd like to read it for sure.

And that bolt.. I'll have to go look. I know what you're talking about now but I haven't ever thought anything of it. Where is that supposed to go exactly

NismoPick

Here's a fresh version of the file. Apparently vBulletin doesn't like holding zip files... If it doesn't work, toss me your email.

NismoPick

I'm also not seeing a clamp on the J-Pipe to air regulator hose (below the left-middle of my red arrow).

ThaPimpShrimp

It worked! Thanks for the files.

Yes there isn't currently a clamp attaching it. As far as I can tell there is no leak there however I'll throw a clam on just in case. I'll check all of my other lines again to be certain as well.

Do you know where that vacuum line that has the bolt in it is supposed to end up?

Also one more quick question for you, I've read that the AAC valve isn't controlled by the z31 setup. I read that it should just be disconnected from the harness I think. Well wouldn't that cause some sort of issue at all? And also if my AAC valve's diaphram is leaking, even if it is disconnected it could cause problems right? I guess I am just looking for an explanation on how this thing works with the z31 setup as everything I've read hasn't been all that thorough.

NismoPick

The AAC defaults to open. When vacuum is applied, it closes. Thus the reason it's hard to keep the L28ET idling when an AAC blockoff plate is used.

ThaPimpShrimp

Right so if the plugs are disconnected from it, it's still working with vacuum then? And if it's faulty it could still hypothetically cause issues. Not saying or assuming mine is just wondering.

ThaPimpShrimp

Fuel pressure when running sits at about 37-38psi.

Fuel pressure with the vacuum line to the FPR disconnected goes up to 44.

And when I shut the car off it settled to about 30.

This is all with a supposedly stock turbo FPR I purchased from RockAuto.. the fuel pump is a walbro 255lb/hr pump.



I do know one thing I have to accomplish this weekend though. I'll be redoing all of the connections made for the z31 ecu swap. They're all just crimped on and not very well. After tugging on them a bit my car wouldn't even start so I figure getting those sorted will at least remove one thing from the list.

The pins and the connectors were as clean as they could possibly be though. New condition which is reassuring. Should I be worried about the actual wire pins that are in the connectors?

While I am doing this over the weekend, anything you suggest I check? (Something about grounds? :P )

NismoPick

I have a few pics floating around of my ecu plug wiring fixes... I'll have to look through my attachments when I have time, but this is one from my photobucket. The grounds I always talk about are the two black ones at the very top. About 4 inches in there is a splice / hub for several grounds. It was corroded and loose so I chopped it out and made a better one.

ThaPimpShrimp

Ah alright I know what you're talking about I believe, I took a look at it today. It's just a mess down there right now so I just need to spend some time getting it all figured out.

When you get the chance any info/picture you have are very appreciated always.

NismoPick

moarz... hella huge pic!

ThaPimpShrimp

Here is how my grounds are set up currently! (Pins 28 and 36)

How did you hook yours up? Or does this look alright to you. Seems pretty solid but I am unsure.



Also, what is this plug here for. It goes into the harness and through the firewall.. I was too lazy to follow it. I guessed the speed sensor or something to do with the cluster?

NismoPick

The main issues are the wire pins in the plug... that's why I chopped mine out and used the Z31 ECU plugs. I also used two eye connectors in place of that stock ground hub. Nut and bolt through the two eyes.

That 2nd plug... not used.

ThaPimpShrimp

Hm alright. I might go with that bolt idea for the grounds.


So here's the deal, I have z31 ecu plugs but I am afraid to do anything with them as I have absolutely no idea what I am doing with them or how they go together and come apart.

How do you get the wire pins out of the 280zx plugs and get them into the z31 plugs without damaging anything? I have a couple inches of wire in the z31 plugs as well.

Edit: Does it matter what year/model the z31 plugs are out of? Also did you change all of them, or just that last one with the grounds. I am not sure if my z31 plug has that white inner layer like yours.. it might.

NismoPick

You don't. Look at my pics...

No. Look at my pics. LOOK AT THEM! Hi.. lol.

All Z31 ecu plugs are the same. You chop the 280zxt wires a few inches back, and solder in the Z31 plugs. Just draw up a colored diagram of each plug wiring and check them off as you connect them. The last few get tricky as all the rest are in the way. And use heat shrink.

ThaPimpShrimp

Haha ah alright sorry! I'm looking now I promise

So you'd suggest me doing all three plugs then huh? Are they that much better at seating? They sure don't make it easy

NismoPick

Start with that top plug with the grounds. That's the one with the most problems. When you look at the Z31 plugs, you can tell they are built better than the 280zxt ones.

ThaPimpShrimp

Just as an update, I see what you mean when you said the z31 plugs are much better put together. They don't wiggle all around and seem more sturdy. I'm about halfway done getting the new plugs in at the moment and I'll finish it tomorrow afternoon!

ThaPimpShrimp

So far I have completed swapping these two plugs circled here for the new z31 plugs. No difference in running yet - still running rich. Is it worthwhile for me to go ahead and do the last one?

ThaPimpShrimp

Here is something to consider yet again. I just got home and I had the thought to unplug the MAF and start the car to see how it ran.

The answer - Idles perfectly. No popping, and no misfiring. Since I've already rewired those two ecu pins I circled above, that should be everything concerning the MAF.

So, that leads me to believe that either my MAF is bad, or for some reason it's reading wrong. (Or there could be another hidden electrical problem - thoughts?)

If I hook up that manual burn cycle to the MAF, that should clean the filament correct? Any idea how long I should leave it connected (just a couple seconds I'd think). Could that burn cycle not going be causing my issue? Anything else I should clean/check on my MAF?

At least this is being narrowed down.

ThaPimpShrimp

Haven't updated for a while because I haven't worked on my car in a while.

So.. hello everyone!! Hope things are going well.


I took the time to check my wiring to the O2 sensor, MAF, and CHTS and I know at least the right wires are going to the right place. Is there a way I can use a multimeter to check if signals are getting all the way to the ecu? I don't know what kind of reading I'd get I guess is my question. I'm specifically looking at pins 12, 26, 30, 31, and 35. I'd also like to check the CHTS and O2 pins..

I also tried testing my O2 sensor in the car. It's a new sensor so it should be good but I think I am doing something wrong? I set my multimeter to 20V DC and put the positive lead into the O2 wire connector, I grounded the negative to my intake manifold. I let me car warm up (at idle) to operating temperature for 20 minutes and never got a reading.

I wish I had someone to teach me all of this stuff :\

NismoPick

The FSM has a very detailed section on testing sensors... especially for the ECCS (turbo) system. Obviously you don't jam the multimeter probes into the ecu plugs. Use a thin gauge wire to jumper between the ecu pin and the multimeter probe. On one of my multimeters I stripped down some telephone wire, wrapped one around each probe, and then cut them at about 10".