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Discussion Starter · #1 ·
So I bought a 1986 300zx turbo a year ago and it has given me like five mounts of great times and a lot of mechanical mysteries. my friend that owns a 280 calls it the witched car. One day it runs sweet the next well, and then without doing anything to it she runs great again. Mine not so lucky. Hoping to find some help. So now I will cruse in my 68 mustang and dream about the z.
 

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Dude if you're driving around in old classic Mustang, why are you even bothering to dream of an old Z?....... that'd be like me being married to Eva Mendez or some other hot chic and then dreaming of being back with my crazy old obnoxious ex-wife haha.... just kidding lol.

Let me tell you something about the Z31... its a problem child! Always needing to be dealt with haha. It's just so over-engineered with crazy stuff that always seem to go wrong. Good job Nissan designers of 1984!...we still love you!
Well, in any case you just need to look at your car and get a proper diagnosis on what's causing the issues. Speaking of that, what is the actual problem that you are experiencing?

Please check out the following website and read up on the Z31 section (you will be glad you did and might even learn some new things about your car in the process)

www.xenonzcar.com

Bon
 

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Discussion Starter · #3 ·
My z has the wrong ecu in it and I cant find the wright one. its a 1986 Z31 turbo 5 speed. today I called the z shop in town they told me that parts for this car are impossible to find so they don't want to see it. Great. True story, so now I feel like I bought a huge paper weight. so I am looking for the wright ECU.
car update. freshened up engine. new rings, bearings, valves reseat, timing belt. compression is good.
new used MAS, tested and good.
new injectors and oxygen sensor.
car starts then surges 400rpm to 1500, untill it stalls. over 2500rpm it runs great
will restart no problem.
 

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Wow. The guys at your local "Z" shop have got to be F*cking idiots if they say they can't source parts for the cars they "specialize" in... either that, or they are young dudes who only have the technical expertise to work on the newer Z cars. I've ran across this problem with Nissan dealerships in some cases- they either don't know or just simply refuse to look at these old cars. So, I feel your frustration. There are plenty of places online to get parts and even locally.
I don't think you bought a paper weight. You've just got some kind of electrical gremlin that is causing these issues (very common on the 300)

How do you know it's the wrong ECU? Have you cross-referenced it?
Was the car having any of these issues before you had the engine freshened up? and did you run the ECU codes to see if any faults existed?
I hope you replaced the CHTS and harness while you were doing the timing belt as that is the best time to get to that part.
Which O2 sensor did you replace it with? The 86T should have the titania if I'm not mistaken and needs to match that ECU.
So you got good compression and it sounds like your fuel and spark is where it should be. This is good.

My best guess right now (if it is not your ECU) is maybe an idle adjustment issue with the valve, perhaps even a TPS issue but wouldn't make sense unless you had the car on the road going full throttle. Have you done anything with the fuel system?
 

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Discussion Starter · #5 ·
OMG So I pulled the EMC just now and found that it was replaced with the correct one 655 M35 by one of my sons friends. he has a few Zs for parts. he had the car for two months trying to fix it with no luck.
I looked at the wire harness to find three wires that have been cut and spliced together at the EMC. Now the fun begins. why where they cut and where do they go.
I did replace the CHTS in to the intake manifold. Just taped into the water jacket and installed a new plug. I did that before the rebuild. it was easer than getting to the CHTS location.
I checked the 02 sensor it is the wrong one. Thanks for the advice on that. I need to order it from Rock Auto.
 

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Yup. It sounds like someone has done some butchy-hackin' on that wire harness... and can explain the weird electrical issues. Are you sure about the O2 sensor? You'll know by the size- the Zirconia is the bigger one with the bigger bung. The Titania is the smaller, skinnier sensor... either way, those must match the ECU and harness, or it will not run right.
Rock Auto Rocks!
 

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1983 280ZX Turbo
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My advice in these cases is to start by returning the wiring to stock, then begin any project you have in mind.
 
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