Z31/300zx ECU/MAF to 280ZXT swap guide

[vega]

needs an update on the pictures as well as a sticky (btw i know this is an old thread)

[Swervey McZCar]

Hoping someone can help. I just finish the z31 ecu/maf swap into my 82 l28et. Im having a poor cold start issue, fires up then stumbles and dies, unless I give it some throttle. Also when fully warmed up, intermittanty it will stumble and die out when im at a stop.

 

I've read some where that after this swap there is a lean cold start issue. I don't have a cold start injector, my timing is at 24 btdc, fuel pressure is at aprox 35 psi. I wired up the ecu and maf accordingly and swapped out injector 5 and 2.

 

Anyone have any suggestion?

 

Did you ever figure this out? I did this swap today and have these exact symptoms. I have a spare MAF I will try in the morning, but I was totally bummed at the outcome. My 84 turbo ECU is blinking all sorts of codes for Fuel Temp sensor, AC, Knock Sensor, etc. Is there consensus that these ECUs will still operate in closed loop withe these missing inputs? Looks like mine is in Diagnostic mode. How can I change that?

 

The swap was very straightforward. Thanks to everyone who contributed to this thread. Now I just need to iron out the wrinkles.

 

 

-Stan

[toan_tech]

Hey Stan, yes I did actually fixed the cold start and hesitating issue. I drilled open the aluminum plug and adjusted the fuel mixture screw by turning it to the right to richen the mixture on the MAF. I also purchased a 3 wire O2 sensor from ebay and wired it up according to the wiring diagram: Black wire to ground, grey/white pin 34 and yellow pin 115. Also make sure all ecu connections are secure. Here is a link for adjusting the MAF http://www.xenonz31.com/AFMCalibration.html. Hope this helps

[RennWerksMotorsports-Mike]

Hey Z heads. Our shop 83 ZX has long since been heavily modified after the 300zx ECM Conversion, but this is what I remember. Before you adjust the MAF, do this simple adjustment first. Set Base Timing of the distributor. Ours had to be almost fully advanced in the slotted holes at the base of the distributor. i.e. rotate the Distributor base counter clockwise. Next, there is a tiny little throttle stop screw on the TB (throttle body) by the return spring linkage. Adjust that to stabilize the car. When using the 60mm 240sx tb, we threaded the throttle stop hole for a longer M4 allen head screw. With the car at operating temperature, Adjust the throttle screw slowly (kinda like a carb) until the idle stabilizes, then snap the throttle and let the computer stabilize the idle for about half a minute. We used a gas analyzer to double check our work, but a good ear and sense is just as well. Connect a Volt meter to the TPS (throttle position sensor). You may have to adjust the TPS after adjusting the throttle plate, to get it back to its proper idle setting. The 300zx ECM has plenty of room in its programming to compensate for the adjustment. Adjusting the MAF should be a last resort in this situation as it can throw your fuel trim off during the entire throttle/load range.

[Swervey McZCar]

Thanks for the advice. I adjusted the timing to 20 degrees and set my TPS after doing the idle and it did help. It is idling pretty smooth, but when I put it under a load there is no go and sometimes a backfire. I was reading the FSM and they mentioned checking the chopper wheel for dust. The chopper wheel I picked up is free of damage and debris, but it does have what look like water stains on it. Does that sucker need to be shiny clean or just free of particles? I will clean it regardless, but I am just wondering if this is the silver bullet.

 

Also, my fuel pump relay is still wired to Key "On" so there is no communication between the ECU and the pump or relay. I figured the ECU would not mind. Am I wrong? Probably.

 

Thanks,

-Stan

[RennWerksMotorsports-Mike]

As long a s the chopper wheel, especially the little slits are free of debris, its OK.

 

Did you adjust the TPS back to factory spec. It should read voltage at idle.

[toan_tech]

I have my fuel pump wired to key on also. It didn't affect my performance. Also check connectors to the ecu by wiggling the connectors. I noticed sometimes when my Z acts up, its due to poor connections to the ECU.

[Swervey McZCar]

Thanks again. I set the TPS to "closed" at idle and "open" just off idle. I am beggining to suspect the connectors more and more. I swapped all of my harness plugs to use the 300zx plugs because my 280 plugs were shot. I had to wiggle them constantly. Sometimes it felt like I was using nitrous when the wiggle was just right

 

Anyway, they were a problem so rather than make 100 soldered connections, I swapped each of the female pins in the connectors from the 280 plug to the 300 plug. I am going to do one more check on my (280zxt) CHTS and them I'll be unwrapping the harness again.

[Swervey McZCar]

I may have found something. I can't wait to try it. I failed to mention that I was running a z31-type coil. I thought I knew + from - but. I think the B/W wire going to this coil is actually on the negative side where-as B/W everywhere else on this car means switched positive. If this is true (can anyone confirm pg 2 in the link below?) I just need to swap my PIN 34 Wire to the L (light blue) Wire going to my z31 coil. I will probably eliminate the PIN3 ground also. Is it that simple or should I really revert back to my L28ET coil and trigger?

 

http://forums.hybridz.org/showthread.php?t=115483&highlight=300zx+condenser

 

I love this "place"

[Swervey McZCar]

I may have found something. I can't wait to try it. I failed to mention that I was running a z31-type coil. I thought I knew + from - but. I think the B/W wire going to this coil is actually on the negative side where-as B/W everywhere else on this car means switched positive. If this is true (can anyone confirm pg 2 in the link below?) I just need to swap my PIN 34 Wire to the L (light blue) Wire going to my z31 coil. I will probably eliminate the PIN3 ground also. Is it that simple or should I really revert back to my L28ET coil and trigger?

 

http://forums.hybridz.org/showthread.php?t=115483&highlight=300zx+condenser

 

I love this "place"

 

Scratch all of this. So wrong of me. After studying the diagrams between the 83 and 84, I am going 1: find a better switched + for PIN34 than coil + and eliminate PIN3 to coil -. It was wet today so I didn't get to do a thing.

[Swervey McZCar]

Well my ECU and MAF were both shot. I had some other parts, and the magical combination of junk yard parts made a car that ran. It's running much better, but rich. I have a 3-wire O2 sensor (84 300zx) and a Fuel pressure regulator (83 280zx) coming in the morning. I "crushed" my last FPR to up the fuel pressure to around 40psi. I was thinking that the combination of these two things would contribute to a rich condition throughout the throttle range.

[stravi757]

Hey guys, Just wanted to say this info was so helpful. I got sick and tired of dealing with my crappy AFM's so out of impulse I went to the junkyard today to get the materials needed and just jumped into this swap without reading much about it until today. I wired the whole thing up in a couple of hours and MAN what a difference did it make. My car hauls now and is running so much better.

[jayzrocket]

Nevermind.

Edited March 5, 2010 by jayzrocket

[ArchetypeDatsun]

When I purchased my 83 280zx turbo donor car I never had the impression that the guy did this swap already, he didn't even tell me at the time all he handed me was a 240sx TB with the adaptor plate, a stock 83 280zx turbo ecu, manual boost control, a BOV with adaptor still didn't know any of this info now reading this helped me out a bit, the car

ran fine with no problems traveling over 300 miles, but when we pulled the motor out to swap it into my 81 280zx non turbo the ecu was the only thing giving the problem, looking at the 83 280zx wiring diagram (not knowing that it already had the 87 ecu & MAF) , but I googled the ecu and it came to be the 87 ecu lol.

Edited April 26, 2010 by 280zx@541

[Blobber]

This might be unbelievably stupid question, but I can't find the answer anywhere(and my engine management knowledge aren't at pro level). I made a L28ET swap and I changed z31 ecu right away. do I need to get ecu chip programmed before I can even make a test start for the engine? I think I do, but am I right?

[stravi757]

This might be unbelievably stupid question, but I can't find the answer anywhere(and my engine management knowledge aren't at pro level). I made a L28ET swap and I changed z31 ecu right away. do I need to get ecu chip programmed before I can even make a test start for the engine? I think I do, but am I right?

 

No. go ahead and try starting it.

[Blobber]

But doesn't it inject gasoline to the cylinder at the wrong time? Because the firing order is totally different.

[stravi757]

But doesn't it inject gasoline to the cylinder at the wrong time? Because the firing order is totally different.

 

your supposed to switch injector clips 2&5(will still run fine if you dont) but other then that your good to go.

[ArchetypeDatsun]

If wanna Mess around with the z31 ecu I believe it's a 16 bits instead of a 8 bits like the 280zxt ecu, the map is way more open and you can make adjustments but I don't recommend it until you have accually driven the car around for awhile I'ma be using Nistune for my z31 ecu way better then using megasquirt, and I really recommend doing this ecu swap for anyone tuning there 280zxt.

 

http://www.nistune.com/

[ArchetypeDatsun]

If wanna Mess around with the z31 ecu I believe it's a 16 bits instead of a 8 bits like the 280zxt ecu, the map is way more open and you can make adjustments but I don't recommend it until you have accually driven the car around for awhile I'ma be using Nistune for my z31 ecu way better then using megasquirt, and I really recommend doing this ecu swap for anyone tuning there 280zxt.

 

http://www.nistune.com/

 

lol sorry guys I'm looking like a fool, don't even know what I'm talking about.