The writeups over on HybridZ are pretty darn good. The main reason I started this thread was primarily because I was/still am a wiring n00b. I wanted some help with a few other things. Primarily I did alot of searching to learn as much as I could. Although I kept running into threads with people having all kinds of problems with their Z31 swaps. Turns out most of them just didn't follow directions correctly. Another problem I think is the fact of the old wiring. Since you start moving it all around, splicing new connections, adding pins, it disturbs it and can leave things open for more issues.

Although the one thing that happened was with both jmmorriso and I encountered. Stumbling, hesitation, popping, bogging etc. It was only at two specific times. In the transition from open-loop(warm-up) to closed loop mode and upon restarting. We also both had the same problem with the control of the fuel pump where it would keep running with the ignition ON. It wouldn't turn off after 2-3 seconds as it should. Even though it was wired correctly I found through the info on RedZ31.com that the 84-85 ECUs have known lean surge issues. Oddly enough jmmorriso's problem was solved when he got the mixture just right by tuning it with a wideband. The other thing that I think helped was the remanned ECU, his fuel pump was now controlled correctly and he no longer had problems at all. By messing with my mixture I got the car to work pretty good, but still had the spots. Over on Zcar people said they had the same issues in their Z31s. There was no amount of new sensors, fiddling with mixture, etc. that got their cars to run right. They finally found on their N/A cars that you could swap to the 87' ECU and it fixed all their problems. It seems like it's luck of the draw with the 84-85 ECUs.

Don't ever ask on Z31 forums for help with the swap. You'll more than likely be told you're stupid and know nothing. Like I was told that when I told them that Z31s used heated 3-wire O2 sensors and that I should put everything back to the way it used to be.

Alright, I've been meaning to do this, but just took a while. Anyway I put the 84' Z31 ECU back in. I ran it without the O2 sensor, it still seemed to encounter the same sort of bogging or slow throttle response, hesitation whatever you want to call it in the same spot as it does with the O2 hooked up. Whereas with the 86 ECU and the O2 disconnected the thing felt jumpy and had power the whole time. I never had a spot where it got slow, bogged, hesitated. So it definitely seems to be the case of the ECU.

Another thing I noticed was with my Autometer A/F gauge. When I was running the 86' ECU there was no bouncing lights, there was just nothing lit up on the gauge as there should be with no signal. For some reason the 84 ECU even with the O2 disconnected is picking up some sort of signal from the ECU. It just sits at 3 bars into Stoich. It's always been that way since I installed it, and never thought anything of it, maybe like the O2 had a base signal, but I noticed it once I started running the 86 with no O2 that there would be no bars lit up. I remember someone else mentioning this same issue on HybridZ in one of the Z31 swap threads.

Interesting! My a/f gauge bounces around a lot too... though it's about time for me to go wideband. I have a spare 85 ecu that I'll have to try out just to see if it makes a diff.

After a little bit it I assume the bouncing back and forth is normal of a warmed up O2, but why it's picking up some sort of signal with Ignition ON and right when I start the car I don't know. From what I can tell it's not all 84-85 ECUs as some people have problems some don't. It is interesting how differently the two act even with the O2 disconnected. I wonder if the 86 had different fuel maps or if that didn't change until 87. I'm still trying to get ahold of an 87' Turbo ECU. As I hear the fuel maps got the change, and the diagnostics are better. I could always swapp the ECU from my 87 300ZXT into my 280ZXT.

I agree with you on the wideband. I've been planning to go wideband, I just haven't wanted to buy one yet. At some point I want to run Nistune as well.

When I had a narrowband, the a/f gauge would bounce back and forth during cruising after the o2 had warmed up regardless of the ecu I was using. The gauge did show 1 bar on the lean side when ignition was turned on too. Maybe it's a self check to see if power is reaching the gauge? Anyway, yeah it's best to get a wideband. Makes it a whole lot easier to keep tabs on the engine and tune. I'm using an AEM wideband which is pretty barebones as far as widebands are concerned. My friend is using a Zeitronix on his 1JZ Cressida and it has a lot more info displayed along with requiring a lot more $ to buy it. :037:

I could figure the 1 bar in lean or something, but it's weird that my 84' ECU is putting out a higher voltage reading about 3 bars into Stoich.

I really think I need to start soldering. I noticed something recently. Every so often when I come to a stop to park or something alot of times my idle will be kind of bouncy or hunting around a bit. Shaking the wires at the ECU made no difference. I then went into the engine bay and I found from what I can tell it's the way I wired up either the ground or the other power wire for the MAF. I can hear an audible change in engine noise when I shake the wire a bit. Or if I just unplug the MAF all of a sudden my vacuum readings go normal, my idle smoothes out, and everything seems pretty good.

I've also noticed if I don't disconnect the MAF or shake the wires, say go into a store,g et gas or whatever. When I start the car back up as I'm just sitting there it will idle really good again. I assume it's just this loose connection and sitting still from a start doesn't allow the wire to shake around and cause my idle to go weird.

How do you have the ECU / MAF swap wires connected right now?

I've connected everything through crimp connections, except for the wire that goes to the ground on the intake, and the wire that goes to the old VCM wire. I figured I'll cut the old VCM wire and just crimp connect to that, and I'll use a crimped connector to ground the MAF to another bolt. I have these two just wrapped around the existing wires and electrical taped.

I fixed the wiring to the MAF so it's better now and does not jump around when I jiggle the wires. My idle is still lopes some. It's probably due to my MAF's calibration so far out of wack. I started playing with the adjustment screw a while ago, and eventually I lost track of the position I was at and have no idea where it started at. I figure once I get the O2 sensor in it will help as well.

I ordered the 3-wire titania sensor, so that's on it's way then I just gotta get it in and connected.

I don't know if the O2 sensor would have any affect on the timing, like if the correct mixture could help the timing, or if the ECU pulls timing because I don't have the O2 connected?

Anyway I was messing around and decided to take a look at my ignition timing. I found that while I'm idling I'm running at somewhere around 12-14 before TDC, when it should be 20. That's kinda wacky and I don't know why my timing got so retarded. The last thing I did was put in my MSD Blaster 2, I don't know if just changing out a coil could cause the timing to change? I know when I put my replacement ignition and a new coil in my timing was way off and had to be reset.

I figured I'd throw an update into here.
Have the nut welded on my exhaust for the later style smaller O2 sensor. I'm running an 86' Z31 ECU. After a long day, mainly for the fuel pump relay and contorting into odd positions into the car I managed to go through and solder all my connections that had been made for the Z31 ECU swap. I gotta finish up soldering the MAF connections.

I couldn't believe how many connections I made by just twisting the wires together and electrical taping them. That's probably why I had so many problems with my harness. The car feels a bit quicker, alot smoother, and it starts up alot better. Before it would start up good, but then act like it was going to die, and it would be a bit odd. So this is a plus!

Ordered Nistune/Wideband, the Nistune is programmed for an 88 Z3T ECU, so that'll be cool.

Sorry to dredge up an old post, but I got another Z31 chopper wheel & decided to compare it to a 280zxt wheel:

http://img.photobucket.com/albums/v4.../CASWheels.jpg

whats up guys?

I decided to do the 300zx swap and am having 1 little hickup that I can't figure out.

I've got fuel pressure, my pump is priming, ecu is lit up, have spark and all my wiring seems to be correct but it doesn't look like my injectors are pulsing.

I've cleaned off my plugs, cranked her over, checked them afterwords and they were still dry.

If i throw the old 280zx ecu in and revert the wiring it'll fire right up.

any ideas or relays that i can just hook up to a ignition source to make it go?

Where'd you get the Z31T ecu? Did you verify that it worked before this install?

car-part.com :D

I'm pretty sure it works because when i unplug my 83 ecu after it's been running and hook up the 300's it will run for a split second then stop.

It's got to be something dumb in the wiring.

i also tried downloading that zip file of yours for a reference but it isn't hosted anymore :(

I attached it in a recent thread: https://www.zdriver.com/forums/showp...8&postcount=44

I would double check the MAF wiring... You grounded it? Changed the chopper wheel? Added the 2 ecu pins? Ran the wire to the fuel pump relay?

I followed all the instructions on the other walkthroughs i found.

maf is grounded and the pins are good. I've been scratching my head for the last 5 hours because this isn't overly difficult and it's starting to eat at me a lil.

i have a 81 setup and noticed your writeup called for a pin added on 114.
what does that need ran to?

Also, just to clarify.. 16 and 108 just need cut and switched around right?

Pin 114 goes to switched 12V power. Does your ecu harness have a wire on 114?

16 & 108 are not "just switched". Pin 16 connects to wire 108. The now cut pin 108 is run to the green fuel pump relay on the passenger side of the dash.

Are you still using the 81 CAS?

no, i have a 83 dizzy with and i swapped the wheel in from a z31's.

Two things I can think of, make sure that you added pin 3 to the ECU plug and that you've added pin 34 to the ECU plug correctly. Then check to make sure you did run the wires to the coil. Pin 3 goes to negative post on the coil and pin 34 goes to positive. If these aren't hooked up I know the car won't start. Although I don't know if that will stop your injectors from firing. The other thing I can think of is do you have the Z31 chopper wheel in the correct way? Finally put your ignition to ON and see if you can run the Z31 Self Diagnostics. It's possible you got a bum ECU, but still hard to say. I bought a non-turbo 87 ECU to put a nistune board into. I opened it up and a section of the board looked like it had been burnt up at some point. I opted not to even bother with that ECU.

i have both of those hooked up and i've messed with the ecu diagnostics and it does it's blinky thing. I'm debating on getting a z31 harness and going from there.

This is just annoying though because it's not a hard swap :P

will pin 114 on the 81 setup keep a engine from starting?