1990 to 1991-1994 Wiring harness replacement

[acidflux]

I've searched for about 2 days now and it seems that there used to be a writeup for this on some ecanfix.com site somewhere. Regardless, I'm having trouble locating a few pieces of information.

I have a 1990 AWD roller in great shape and a 1991 car that was flipped, but still runs. I want to pull the engine/trans out of the 1991 and stuff it into the 1990 car. My plan is to also pull the wiring harness out of the 1991 car and also put that into the 1990 car as well so I dont have to hassle with buying a mix of 1990 and 1991 sensors and parts whenever the car breaks down.

So... what does the wiring harness connect to in the cab of the car besides the ECU and the MPI relay? The 1991 car has ABS so, I'll be ignoring that section. Basically I don't want to rip all this to pieces and reinstall it only to find out that I have a bunch of mismatched connectors in the cab that wont directly plug and play with the 1990 stuff.

Next comes the tranny/tcase. I know they are different, so... can I just swap in the tranny and tcase from the 1991 and just swap the shifter cable brackets and go or do I have to swap the shifter assembly too? Will the 1990 axles go into the 1991 tranny?

Thanks in advance for your thoughtful, accurate, and helpful replies.

 

[Auto RS T]

I can help you along with this swap. Its very do-able. Only a couple connectors are different in the cab. as far as the harness is concerned. The axles are the same and if you use a matching trans and transfercase either will work with their respective cables.

 

[acidflux]

Thanks for the straightforward answer! What's involved in-cab? Anything tricky or does it all directly plug and play?

 

[acidflux]

Anybody else have any input?

 

[92AWDHX40]

Just swap the entire harness into your shell somethings are differnent pull it all out and swap it, 90 91 is different.

 

[Auto RS T]

Using all your 91 parts and 91 engine harness.

TACH

If you want the tach to work correctly while maintaining the original 90 body mileage you have to take the instrument cluster out of the 91 dash, take it apart and swap the tachometer with the 90 unit and use the 90 cluster obviously. The tachs just unsrcew from the clusters once everthing is apart.

TRANS

90 - 22 spline output shaft for the tranfercase
91+ - 23 spline output shaft for the transfercase

Either set of axles or the driveshaft will work. Use the better of what you have.

91 trans must be used with 91 transfercase, or 90 trans with 90 transfercase and the shifter/cable setup that belongs to them.

So, in order for the 91 transmission and transfercase to work correctly remove all shifter components from the 91 and use them. Leave the cable bracket on the 91 trans, use the 91 cables, and unbolt the 91 shifter assembly from the floor pan and use that as well.

When you get to the harness I can go into more detail. I'll need to look at what all you need to do again to help you accurately, its not too bad.

 

[acidflux]

Now that's what I call an answer! Yeah, that all sounds very straightforward and easy, I've done it all before at one time or another, between the various DSMs I've had. Never done any 90 converting though. Like I said before, I have no idea what the wiring harness goes to once it's inside the cab besides the ECU and the MPI relay. I've never pulled a harness...

Tonight's mission is to get the engine/trans the rest of the way out of the 1991 car. It's about 1/3 of the way there already, just gotta keep picking away at it. I got the engine/trans out of the 1990 car already and removed the a/c system. Not too shabby for 2.5 hours monday, 3.5 hours last night and whatever I wind up with tonight.

 

[acidflux]

Ok I got both engines/transmissions/wiring harnesses out of both cars and partially installed the 91 wiring harness into the 90 car. There are 2 connectors in cab that dont match. The one by the passenger side door has all the right wires, just the wrong connector, I already took the pins out and am going to finish swapping plugs tomorrow. The mystery is the plug by the ECU. There's the 3 plugs for the ECU, the plug for the MPI relay, and the mystery plug that has a different number of wires than the plug in the car. I compared harnesses side by side and it seems to be that the 94 harness has like 4-5 extra wires in that plug. I have no clue what that plug goes to or does so... I guess that's where I'm at.

Tomorrow's goal will be to drop the engine/trans/tcase into the 90 car and get everything buttoned up. I'll tackle the in cab nightmare after I get the easy stuff done. It's kinda scary when I think of a motor swap as easy nowadays

I kinda had a revelation in my dreams about that mystery connector. It seems to be the only one that is close to the gauge cluster, and those gauges need information from somewhere right? That has to be what it is. I guess I'll do some research and figure out what I have to do to get the wires set right and see what's missing/etc. I bet those extra wires are for ABS...

Anybody have any input?

 

[Auto RS T]

I believe that plug has something to do with the Data Link Connector next to the fusebox. I'm working right now but can help you with more details again later tonight. We have a busy race weekend here but we'll get you helped out.

 

[acidflux]

Thanks again, your help is greatly appreciated. I should have it all together and possibly running tonight, pending that mystery plug's significance to having the engine run. I think I'll be fine but we'll see...

UPDATE: I took both plugs from both harnesses side by side and obviously most of the wires were the same so I swapped them over to the matching connector and left the miscellaneous unknown wires just loose taped up. I plugged everything in, fired it up and everything seems to be running within spec, at least as far as wiring goes. There is a problem somewhere (probably due to my emissions delete) that is causing the car to bog almost like a no fuel condition when you hit the gas pedal, which only lasts for a second or two, then it roars to life. Almost like a delay... gotta be a vacuum leak somewhere...

 

[acidflux]

Ok final update. Since the car had been sitting for 6 years, the gas had gone bad. I put some fresh pump gas in it and it's been purring like a kitten ever since. Sadly now I have a cooling issue to figure out... that's all easy stuff though. Thanks again for all the help and input, you guys ROCK!

 

[shift2drift38]

Perfect topic here! I'm also doing tearing down a 1991 Talon, pulled the motor and trans, but as I was removing it I noticed a lot of ports were blocked off...that made me believe this could be a turbo motor, since some of the cooling ports and an oil port from the left side of the head were blocked off. Persay this "is" a turbo motor, I noticed the car I'm putting it into, a 1990 Eclipse GS, (non turbo setup for sure) does not have the plug to hook up to the CAS currently on the Talons head. What gives? Do I snip it from the Talon harness and wire it in the 90's somehow?

 

[19Eclipse90]

What gives is that's one of the 1990 model vs. 1991+ model differences and has nothing to do with the engine being turbo or not.

The easiest thing to do is to swap to the CAS that the harness has a connector for -- if, by chance, the CAS is/goes bad, unplug it and throw in a new one as opposed to wiring up another one. Check page 6 of this PDF or simply scroll down on this website to see the different 1G CAS units.

Any of them should work; if you don't have the correct CAS for the harness wire it up if you must, match the colors and solder away. Make sure you install it correctly (not 180 degrees out, engine at TDC) and that you reset your ignition timing (Base Timing Adjustment or Engine Timing).

 

[shift2drift38]

So if I just buy one for the harness I have ( 1990 ), it should just plug and play on the 1991 head? From what I read on your links, that's what it's saying... I think . Thanks for the reply!

 

[19Eclipse90]

Yes.

Wow, I need to pay a bit more attention to my morning posts. That thing was confusing as all hell.

 

[shift2drift38]

And this is why I rely on DSMTuners, you guys are awesome. Just bought one for 60 bucks shipped, not to mention, I'm buying my first GSX, 1990 no less this weekend! Thanks for all the help!

 

[shift2drift38]

Well now that have my 90 GSX and am pulling all but the wiring harness from the donor car (1991 NT Talon), I noticed my GSX's ECU is gone...so, would the 91 Talons ECU work or do I need to find a 90 GSX ECU?

 

[19Eclipse90]

It may start the car, but it won't run properly. You need another manual transmission, turbo ECU. Another 1990 ECU would be ideal, but any 1991-1994 ECU will get you going (after switching pins 6 and 14 at the ECU).

 

[shift2drift38]

The GSX came with the transmission setup, just no engine or "guts" (only thing left in the bay was the harness and brake booster >_<) So really all I'll need is a Turbo 90 ECU (unless I go the 91-94 route), and will it matter if it's from and Auto or 5speed Turbo?

 

[19Eclipse90]

I see that came off a bit wrong; I meant a turbo ECU from a manual transmission vehicle, not that you needed the manual transmission itself. There were no 1990 automatic turbo vehicles.

Again, ideally, you want one from a manual transmission vehicle because of the difference in fuel maps compared to the automatic vehicle's ECU. One of those will work to get you going, but not as well as an ECU from a manual transmission vehicle.

 

[shift2drift38]

Alright then. Thanks alot for sending me in the right direction!