Harness swap difficulties.

[brtmsx]

Ok, so heres the downlow.

I recently purchased a 92 TSi (AWD) shell and am in the process of swapping the engine, ecu, and engine wiring harness from my old 90 TSi.

Now I'm sure most of you are wondering why the f*ck I would be swapping out the 92 harness for the 90 but to be quite frank about it, I'm broke and the wiring harness that was in the 92 looked like a guy with cerebral palsy and epilepsy put it together while sitting next to a strobe light.

Now with that out of the way, I've managed to get everything wired up except for one plug. It's the large white plug (on the 92) behind/next to the ecu where the engine wiring harness and dash harness meets. The problem is the 90 engine harness plug is far smaller (and far fewer wires) than the 92.

I have a pigtail i could splice onto the 90 harness but I'm really not sure what the extra wires on the 92 harness are for and if it would cause any more issues if I were to just tape them and leave them.

If anyone can offer any insight on this it would be greatly appreciated.

And if I'm not being clear about this, I'm basically doing the opposite of a 91+ harness swap in a 90.

Also, I'd really like to keep from hacking up the dash harness in the 92 if at all possible as i will be swapping a 91+ ecu and harness back into the car just as soon as my wallet allows me to.

I also attached pictures of the plugs, the first two are of the 92 dash harness plug, #'s 3 and 4 are of the 90 engine harness plug and #5 is the 92 pigtail as labeled.

Anyway, thanks in advance guys!

 

[skatershawn]

Everything should plug right together. Except the MPI relay.. which is a little gold box bolted next to the ecu. That is different on the two models.

 

[brtmsx]

Yeah, the connection for the relay was fine. The connector I'm referring to would be C67 on these diagrams.

1Gb DSM 4G63 Turbo Wiring Harness Diagram

the wires on the 92 harness (c-67) are as follows,

Pin 2: Red&black w/blue dashes
Pin 3: Red&black
Pin 5: Green&white
Pin 7: Green w/red dashes
Pin 8: Red&green
Pin 9: White w/red dashes
Pin 10: Yellow
Pin 11: Blue&red
Pin 12: Black&red
Pin 14: Black w/orange dashes

which in comparison to the 90 harness just leaves the
green w/ red dashes,
green/white,
and black w/ orange dashes
as the odd men out.

does anyone know what these are for or if it will cause me headache in the future if theyre left disconnected. ive poured over the factory service manual for the last 2 hours but apparently im quite awful at reading wiring diagrams.

I know they're all related to one of the following 4 things, cruise control, mpi, power windows or ac.

But honestly idgaf about cc or ac so if the 3 "extra" wires are related to either of those then were all good, but as stated above im awful at reading wiring diagrams so im not 100% sure what wire is for what. if there is a wiring guru out there that could shed some light on the subject id greatly appreciate it!

Resolved:
green w/ red dashes - not needed idle switch to cruise
green/white, - not needed tps to cruise control
and black w/ orange dashes - not need cruise also

The easiest way to do it is depin the 90 harness first, and one at a time depin the 92 harness replacing the wires with the same color combo. There will be 2 red with black. One is for AC clutch relay, the other is for backup memory. the one for backup will be bigger than the AC clutch relay, so match it to the bigger gauge wire on your 92 plug.

 

[gsx7707]

so you can change the harness under the hood without any splicing?i had a fire and burned alot under hood mostly wiring.is this real bad or fairly easy?i will need to do all wiring under hood. thanks for any help