Hi I am doing a swap from a 91 trans am GTA with 5.7 TPI to and 85 trans am that was set up with a 5.0 TPI. My mechanic that is helping me with the swap says that 85 has mass airflow sensor and the 91 motor runs speed density sensor. The motor is in the 85 now and trying to get it wired up. Does the wiring harness have to be changed? Or are there ways around this? And will the computer still work from the 85 or does that need to be changed as we'll? Any help with the electrical would be greatly apreciated!!

 

Yes, use the 91 harness & ECU. Not only would you need to completely re-pin the harness, but you'd need to add more signals that aren't in the 85 harness. On the other end, you'd have to move a bunch of stuff around because the 85 v-belt system and 91 serpentine system put the alternator & ac compressor on opposite sides. Then there's the different distributor, the single vs. dual fans, blah blah blah. You can swap harnesses in a couple hours, and it's well worth it. It will be easier in the long run to use the 91 distributor, fans, & radiator shroud (fan mounts) & lower fan mounts. The only issue that you're going to run into with using the 91 harness is that the battery & charcoal canister are on opposite sides between those 2 models, but those are both pretty simple to rework.

Swapping over the 91 harness & ECU will save you huge amounts of aggravation trying to make the stock harness work, and with respect to the ECU, there's no way the 85 ECU would work unless you retained the 85 MAF setup, but you don't want to do that anyway. The 85 ECU is a dinosaur and has very little support from the tuning community, and you WOULD need to retune for it to run a 350 properly.

 

Thank you so much for the help! Sounds like I got some work to do will keep you updated on how it goes! Thanx again!!

 

Hi just another follow up question. On the firewall plug near the brake booster do any of the pins need to be relocated running the 91 harness?

 

http://berlinetta.info/C100.htm
If you need any reprograming assistance , remove vats ect send me a pm

 

If you had installed the 85's TPI set-up on the 91 block than the only changes you would have needed to make are to replace the distributor gear on 85 distributor, a set of 350 injectors, a sensor or 2 ( knock, Oil Pressure, ESC? ) and a 85 350 PROM.

Since your going to use the 91 harness there will be changes in the wiring and you'll need to use the 91 SD TPI parts. Just take your time and you shouldn''t have a problem.

On top any C100 changes from 85 to 91,...... Your're also gonna' need to do some wiring work to the ECM/Dash C207 ( & C221 on the 85 harness) connector too. I'm not sure exactly what's there and what's not - at a minimum, I know the injector wires are not in the same spot and that you will need to modify or eliminate the VATS .

http://berlinetta.info/C207.htm

 

Everything from the 91 was used.harness and all. I have a 91 gta that's got wrapped around a telephone pole when I bought it. Recently got an 85 in great shape with no motor or tranny. So I did the complete swap. My mechanic is having issues getting it all wired up. I'm not much help with all the fuel injected stuff does anyone know anywhere he can call to pick someone's brain? I'm sure he would understand a lot better.

 

He could always come to this website with his point-directed questions, or get the wiring diagrams out of the 85 and 91 service manuals.

 

Thanks so much for all the help!! I hate to keep asking questions but does anyone have a wiring diagram for the firewall plug by the brake booster?? On 85 and 91. My mechanic has no idea how to modify and is debating ripping out the 91 and running the 85 harness instead. And from what I hear is not the way to go..

Thanks again everyone!!

 

here is another link to C100 pinouts

http://www.austinthirdgen.org/index.php?pid=19

 

OP listen to this dude he's been there

 

Well here I am again with the same problem only I'm dealing with a retard mechanic who doesn't know if his *** is punched or bored. You guys have ben very helpful to me and I want to take a minute and thank everyone for all the help to further my story my father owns a repair shop where his mechanic that I am paying on a side job to do my motor swap is "stumped" with the pin out change from the 85 car trying to plug in a 91 harness. He says that there are extra pins in some locations and missing pins in others and all the diagrams, manuals etc doesn't spell it out for him in dummy terms. I wish I was better at this sort of thing but I'm a metal fabricator by trade and my T/A as my passion/hobby. Everything is complete accept for that one grey area behind the master cylander. I have debating pulling the project before he efs it up even more. But if someone can dummy it up for me I might try and tackle this final step myself(can't be rocket science) if anyone can point me in the right direction I would forever be in your dept

Thanks so much again
Brad

 

Brad: there ARE wires and pins that will not cross over, that is somewhat normal. where are you located at, and give us the ECU numbers that you are using, with that??? Aw crap dude!!! just had an epifiney!! I think the majority of your wiring woes could be eliminated if you used the 91 ECU and wiring, it would feed through the fire wall and all, the only repining would be the "clear" plugs behind the glove box. at least the Camaros would be that way.

Tuned Am I right on this??? it has been a while for me???

 

Your right Tinbinder, The differences are in c201 can c100 . its very straight fwd. just print off the diagram pic of the 85 and 91 c100 and c201. Mark on the picture what lines up. What doesn't match change the position bye repining. One piece of information you will not run across is the optical vss signal going through c201 a brown wire to a10 of your 85 1226870 ecm will now goto c6 of the 1227730. the memcal needs to be reprogramed anyways to disable the vats , the vss input can be changed to optical.

 

Brad Tuned Performance is your man, PM him and he is always happy to help out.

 

just put the 91 interior harness inside your 85. Problem solved

 

that is easier said than done I 'm not sure of the compatibility of the rest of the interior electronics

 

I'm sure the dash just falls lout lol

 

I mean that way you dont have to mess with the engine harness anymore. And im sure you could find stuff to do while you have the dash apart.
-heater core
-new speakers
-stereo
-fix blendor

the first thing i did with my camaro when i got it was rip the dash apart and i only thought about lighting the car on fire like once a day twice tops.

 

Had you left the 85 MAf parts and wiring in place the car would probably be driving by now. The decision to convert to SD TPI is the biggest reason for the slow progress that your dealing with. IMO: If the 91 harness is still in a box,... I'd leave it there and start bolting MAF parts back on the motor and use the original harness.


This is the approach I took when installing a 90-92 3.1 engine into an 87 2.8 Coupe one time. By using fully compatable wiring the engine swap was more 'Plug-&-Play'. ( also used 90-92 wiring @ the back of the car.) BUT: I did have to modify the body in order to install the 90-92 dash housing/harness into the 87,..... The dash brackets that are spot welded to the body are NOT the same.







Here is the C100 for your 85




Here is the C100 for the 91







Here is the C207 connector for your 85

1985 C207


PIN Color From / To (Notes)
A Brn ALDL (pin C) / ECM (AIR control)
B* Dk Blue BU Fuse / Back Up Switch ( V8 T5 )
B* Red ALDL / Fuel Relay ( V6 - TPI )
B* Org/Blk FP FUSE / Fuel Relay ( L4 )
C* Brn/Wht ECM / CE Light ( L4- V6 - TPI )
C* Wht/Grn Light Driver / ECM ( LG4 & L69 )
D* Blk/Org FP/INJ fuse / Fuel Relay ( L69 )
D* Tan/Wht Fuel Relay / Fuel Pump ( V6 )
D* Lt Blue Fuel Relay / Fuel Pump ( TPI )
D* Tan Oil Pr Sensor / Oil Pr Gauge ( L4 )
E Wht/Blk ALDL / ECM (test)
F Pnk/Blk IGN fuse / EGR-ECM
G* Dk Blue BU Fuse / Back Up Switch ( V8 T5 )
G* Pnk/Blk Gage Fuse / MAF Relay ( V6)
G* Pnk/Blk Gage Fuse / Burn Off Relay ( TPI )
G* Pnk/Blk Gage Fuse / Air Cond Relay ( L4 )
H Tan/Blk ALDL / TCC-ECM
J* Ppl Starter / Fuel Relay ( L69 )
J* Org ALDL / ECM ( L4 - TPI )
K Brn ECM / VSS
L Tan/Wht Fuel Relay / Fuel Pump ( L4 - L69 )
M Blk/Wht VSS,P/N switch / Grd
N Org/Blk ECM / P/N switch
P Ppl Brake / TCC
R Ppl/Wht Crank Fuse / Cold Start-ECM ( V6-L4 )


Plug C221

A Pnk/Blk Inj2 Fuse / Even Fuel Injectors
B Lt Green Back Up Switch / BU Lights ( V6-T5 )
C Brn Fuel Pump-Fan Fuse / Fan Relay ( V6 - TPI )
D Pnk/Blk Inj1 Fuse / Odd Fuel Injectors
E
F Dk Blue Back Up Fuse / Back Up Switch ( V6-T5 )


Here is the C207 connector for the 91
1990 - 1992 C207

PIN Color From / To (Notes)
A Brown ( TBI )
B* Pnk (Red) INJ1 TBI (TBI)
B* Pnk/Blk INJ1 (V6 / TPI)
C Brn/Wht ECM / CE Light
D Grey Speed ECM to Cluster (Not with TBI)
E Wht/Blk ALDL (pin B) / ECM (test)
F Pnk/Blk ECM fuse / ECM
G* Pink/Blk (white) INJ2 TBI (TBI)
G* Pnk/Blk (INJ2 V6 TPI)
H* Tan/Blk ALDL / TCC-ECM (auto)
H* Tan/Blk ALDL / Upshift (stick)
J Org ALDL (pin E) / ECM
K Brown ECM / Buffer (Only TBI)
L Drk Blue Vats to ECM
M Org Interior Lights
N Org/Blk ECM / P/N switch
P Red Speed Sensor (Not with TBI)
R Ppl/Wht Crank Fuse / Cold Start-(only TBI)


If your 'firm' on converting from MAF TPI to SD TPI then print that info out,..... you've got some home-work to do !

 

Well everything seems to be moving forward with the car now but running into some issues with it running. Cranks fine and if you put fuel directly into the throttle body it runs till it's gone..There's no power to the fuel pump but if you hotwire it, it works fine..but there is no injector pulse. Not the ignition module The distributer and fuel pump both new and have spark and fuel pressure. Could that be related to a missing ground? Or the pin outs? Is my mechanics question. Hope this makes sense to someone haha

Cheers!

 

Keeping in mind also that it's a 91 motor/tranny and harness in an 85 everything else

 

I can only assume that you programmed the VATS out of the ECM ??


Here is the wiring for the 85 Fuel Pump as it was before you started:





Here is the winring for the 91 TPI fuel system:








The wire from the relay to the FP in the 85 runs thru C207 ( Pin D, Dash-to-ECM harness on pass side) then thru the 85 Body narness to the fuel tank.

The wire from the relay to the FP on the 91 runs thru C100 ( Pin G4, Dash-to Engine ) then thru the 91 Dash/Body harness to the tank.


You will need connect everything together properly before the FP will work as designed.

 

How do you program the vats out of the ECM?

 

https://www.thirdgen.org/forums/tech...elay-vats.html

 

Now I don't have a chipped key or the steering column that requires it. Cause it's the 85 stuff there. Is that an issue?

 

So from the research I'm doing. You can jump some wires over and it will bypass? Is that correct?

 

It is a lot more work but you can install your passkey module and a resister to make it function.

 

My problem is I don't have any of that would it be easier now to swap back over the 85 harness and just run MAF. I'm kinda just throwing my hands in the air now cause I don't know what to do with this vats.

 

Have it programed out or install this !
http://www.ebay.com/itm/GM-VATS-or-PASSkey-II-Bypass-Module-For-LS1-and-LT1-/281179660936?pt=Motors_Car_Truck_Parts_Accessories&hash=item41779d2288&vxp=mtr

 

Ok excellent! Just purchased one. Are they easy to install? Do they just connect next to the ECM?

 

The 30hz signal goes to pin F10 of the ecm. Gnd, accessory pwr
http://www.productmanuals.biz

 

Honestly I feel like it would be much easier for me to do the reprograming and use the optical vss signal from the speedometer. You will need to install this if your are retaining the 85 transmission.
http://www.tpiparts.net/inc/sdetail/7587

 

Ok fair enough! I will be using the 91 tranny. Have good crank on the motor now just the injector pulse giving me issues. Hopefully that module will solve at least one problem

Thanks so much!!

 

That will do the trick, you must be swapping dashes or installing a aftermarket speedometer. I must of overlooked that in the thread.

 

Oh ok! I was not aware of the spedo. Now I have everything from the 91. Would I just need to swap the clusters? Or will in not wire in the same to the dash?

 

I'm not sure on the dash question, you might want to ask member john in ri he would know for sure

 

The ONLY way you could use the 90-92 dash cluster is if you swap the whole housing by removing the entire 85 Dash housing/wiring, drill off the original dash housing mounting brackets and re-install the proper 90-92 brackets. ( as shown in post #20 ) Be aware that if you convert the dash then you are well advised to also swap the Headlight Harness and Body Harness if you are going to convert the dash from 85 to 91 style so that all the wiring is COMPATIBLE.

Not sure why you are messing with the existing Speedo now??

To get your original 85 Speedo to work with the 91 tranny simply install the original VSS from the original tranny into the replacement and then install the adapter/converter that TunedPerformance has already told you about.

http://www.tpiparts.net/inc/sdetail/7587

 

Oh fantastic! That seems like an easier way to do it lol! I would prefer to keep as much as the 85 as possible including spedo cluster to get collector plates on it. Cause it was stock with the TPI motor. Just gotta pretend its a 305
Thank you so much for all the GREAT help!!!

 

No problem ,.....

& good Luck with your build !

 

Leave it to big bad john

 

They may be few-&-far-between,.... but I have my moments !

 

So back to the VATS bypass. I have the signal that goes to f10. Dark blue wire I'm assuming. Is there any recommendations to where the acc power should come from?

 

The bypass isn't drawing much power at all you can tap onto a6 a pink/blk wire, ground to the dash frame or d6, d7

 

Any ideas about the control wire aswell?

 

30hz the control wire is not hooked up, iirc its 30hz expected signal at 50-60%

 

Hey just another follow up question With the bypass module. My instructions seem pretty straight forward, only confusing part is locating the F pins. It says on the 32 pin connector. I found that no problem but nothing labeled "F" if I count the pins I see dark blue in 10 which I believe is the anti theft. Do I just connect it to the dark blue wire? Then acc power/ground etc. and do I just need to plug it into the base of the pins?

Thanx so much yet again!

 

Or if anyone has a picture of what it looks like installed would be even more fantastic! I always get nervous when it comes to electrical

 

 

I hate scotch locks but in this case it might be the easiest.