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Old 08-01-2007, 10:16 PM   #1
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Default Wiring prep for MS

I've posted a question about this before, but now I'm really interested.
I mutilated my wiring harness during Bipes/02clamp install, and when I remove them for MS, I'll want to make everything right again.

Questions:
How do I tell if I've got a 49/50state car? (searched and couldn't find).
Is there a dif between 49/50state harnesses?
How hard it is to remove/reinstall the wiring harness with the dash in place?

Does anybody have a pic of a complete harness? I really only need the last 10 inches at the ECU connection, but I'm not doing any more soldering on my knees... I can barely solder at the table. I might just buy a complete replacement harness if I can find one.

I'm pretty sure what you see in the pic is what I want... although this one is for an '01.
Does the 90-93 look like that? If so, it doesn't look like a big deal provided unhooking things behind the dash goes well.


Last edited by samnavy; 08-01-2007 at 10:57 PM.
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Old 08-01-2007, 11:11 PM   #2
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Hey Sam, I think you are over thinking this one. As far as Bipes removal goes, you'll need to pull it out and reconnect the CAS wire. Solder and heatshrink would be best, but you could also just use a butt connector. A butt connection made with a crimp tool (not a plier) is pretty strong. I always wrap mine up in electrical tape too, incase the wire is ever tugged on. Either type of repair won't take you 5 minutes.

For your o2 clamp, just cut the wire between the ecu and clamp. You'll not need your NB sensor at all with MS. Instead, you will hook up the analog out of your lc-1 directly to the nb wire. You'll have another 5 minutes worth of work here.

I think the 10 minutes you'll spend cleaning up your old harness would be a much better idea than dealing with replacing the harness for a virgin one.

Something that I've been having to deal with is ground issues. It may not end up being necessary on your car, however I would recommend you proactively clean where your ecu grounds on the head, right by the fuel rail. Pull the bolt, scuff up all the metal on the head and on the ring terminal until they are shiney, and replace everything. You might also check out FM's Link installation manual (pdf download from their website) and follow their ground recommendations for the Link.

On top of cleaning up the ecu ground, I've also found that my MS likes to have its own +12V and ground wires. Previously I had my gauges and wb controller all sourcing power and ground from the ecu harness, but I was getting some random misfires. Since running the accessories seperately, the misfires have cleared up.

The ground work may not even be necessary, but you're looking at very little extra work. It made a big difference in my car.

I'd also recommend getting the vari-TPS. Mine is an aftermarket model that was around $40. Atl93le got his for cheap off ebay from a 735BMW, which is supposed to fit on the miata throttle body w/o modification.
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Old 08-01-2007, 11:14 PM   #3
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Atl93le got his for cheap off ebay from a 735BMW, which is supposed to fit on the miata throttle body w/o modification.
Same plug and everything...although I'll report back sometime soon about whether it is in fact usable. But if it, I'd warrant it a great $5.
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Old 08-01-2007, 11:28 PM   #4
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Ben, I totally hear what you're saying. Thanks for taking the time for a long post. The problem I had when I installed the Bipes/Clamp (the reason the job is so hacked up) is because I have no room to work in there. There's no way I can clean it up or do good work bent over on my knees... at least not to my satisfaction. I've got to get it out of there so I can comfortably work on it.

I've decided at the very least I'm going to remove the current harness and completely repair it. I'm wondering if there are any hard-to-reach connections or things to be careful of breaking?

Vari TPS is in the plans. I'm doing initial MS homework now and intend to go PnP. First I've gotta solve my clutch slippage issues, but after that, it's time.
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Old 08-02-2007, 10:02 AM   #5
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I've seen your pictures and understand how ---- you are. But let me use your own logic against you.
You want to spend the least amount of time possible on your knees. ( :gay: )
Fixing your harness should take on the order of 10 minutes. All work is at the passenger's footwell.
Replacing the entire harness will take a long time, and will have connectors scattered about. And will have more opportunity for problems as you'll be touching every electrical connector from the ecu, instead of just 2 wires.

You are taller than me, but I am 210 lbs, with a very bad left knee. I got in there to fix my wiring. Assuredly, you can do. I don't see you doing yourself any favors by making a job more complicated.

BTW, MS install requires you to be in the passenger footwell anyway, running some wires and a vac hose through the firewall.
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Old 08-02-2007, 10:02 AM   #6
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Quote:
Originally Posted by samnavy View Post
I'm pretty sure what you see in the pic is what I want... although this one is for an '01.
Does the 90-93 look like that? If so, it doesn't look like a big deal provided unhooking things behind the dash goes well.

I dont even want to think about how much of a PITA it will be.....
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Old 08-02-2007, 12:04 PM   #7
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Originally Posted by samnavy View Post
Is there a dif between 49/50state harnesses?
There is for '93, but it's not going to much matter since you're rebuilding and going MS.

The difference is that '90-'92 and '93 Fed cars have two injector drivers at the ECU, and run the injectors in pairs. '93 CA cars (and all '94+ cars) use four injector drivers.

My understanding is that the MS has only two injector drivers anyway, so even if you do have a CA car, you're going to need to convert back.

Easiest way to tell the difference is to peel open the injector harness. If you have three wires (Red-White, Yellow, Yellow-Black) feeding the injectors then your '93 is a Fed car. The presense of Green and Green-White wires as well means is a CA car.

Actually, it's probably easier to inspect the wiring at the ECU, but I don't have a '93 CA wiring diagram at hand and so I don't know what connector positions are in play.
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Old 08-02-2007, 02:04 PM   #8
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I dont even want to think about how much of a PITA it will be.....
I have seen a friend who is the most ---- person I know do it. It took quite a while and involved removing the dash and most of the interior but It can be done.
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Old 08-02-2007, 10:36 PM   #9
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Ben, I will be running my own ground wires to help avoid the problems you are talking about, but as far as power goes, do you really feel its necessary to run a separate power wire for MS? I mean, if the MS PNP can use power and ground from the stock wires, I would think its possible to use them as well without issues.
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Old 08-02-2007, 10:45 PM   #10
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no I don't think it is necessary to run a new power wire to the MS. If I was unclear, I mean to say that you should not power other devices (gauges, wb controller, ebc, whatever) off the ecu power and ground wires. Get switched +12V for the gauges n stuff from a different circuit, and run a second ground wire for them. But ground them at the same point on the head, just through their own parallel wire, clean the ground point at the head, and also probably do the ground mod as described in the Link installation manual.

I had my wb gauge and wb controller using the ecu's +12V and ground. I thought it was the proper thing to do at the time, but random misfires caused by sharing power proved me wrong.
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