View Full Version : 90 celica 2.2 swap to st185, need help

02-25-2011, 04:40 AM
hey guys, i have a 90 celica gts and just bought an st185 motor. my engine harness goes through the firewall on the passenger side and the st185 harness enters on the driver's side since it was from japan. how can i connect the harness through the firewall? i've heard you could drill a hole or extend the harness? is it going to be difficult to extend the harness or am i better off drilling a whole?if i do extend the harnes, what size gauge is the wire?if i drill the whole will the harness reach the ignition? any input would be appreciated!

02-25-2011, 10:41 AM
I have never done the swap myself but I have a feeling you're going to have to extend the harness no matter where it enters the firewall. Do a search and see what you can come up with. Good luck.

02-25-2011, 04:04 PM
If you'll look in the forced induction forum you'll find information that will help you with the swap. Or Dr Tweak also does harness conversions for a reasonable fee.

02-25-2011, 04:08 PM
Technically, you can do either. Many people here have done both. However, I'd suggest a 3rd option.

De-loom your harness, and move / extend the wires that are needed to go through the firewall on the passenger side. Basically, they would just need to "flip" over to exit on the other side of the intake manifold plastic wire guard / cover. It's a bit of a task, but I bet it is faster than extending the harness, and certainly cleaner than drilling a big hole. Also it will give you a chance to wire in the 3rd ECU plug.

To answer your other questions:

Wire gauge: depends. Some are thick, some thinner, some are shielded.

Will it reach if you drill: yes.

02-25-2011, 05:00 PM
wow, thanks a mill. ive been searching threw forum after forum looking for that answer. all i kept hearing was how to swap a 185 into a 165. i just spent about 2000 on the engine with the uncut harness and ecu included. im using my fwd tranny for now. im not looking to spend to much more so if i did the extension i would prob do it myself. problem is i never spliced and soldered wire before so im not looking to mess up the harness. im probably going to drill a hole but what did u mean when u said it would give me a chance to wire in the #3rd ecu plug?

02-25-2011, 05:37 PM
I drilled through the firewall just above where the shifter cables enter the cabin, then get some type of rubber grommet to seal it off

02-25-2011, 05:46 PM
did the harness just reach or did u have plenty of play with the wires?

02-25-2011, 11:09 PM
I have my harness run through the same hole that the shifter cables run through. There's plenty of room.

If you go that route I would recommend doing as I did to make sure the loom is water/oil tight. Wrap the insulation with a wide roll of 3m electrical tape. Do a couple of layers. Do this to the loom where it enters the shifter cable hole and up to the manifold area. Just a few feet worth. Then wrap a piece of plastic wire sleeve over that area.

I used some Firestone EPDM compound to seal the hole. That's something you would have to buy from a roofing company. You could also buy a neoprene roof vent boot from Home Depot or Lowes to seal the loom to the shifter cable hole.

You will have to extend the AFM wire harness by 8 inches and relocate the diagnostic box. You'll also need to rotate the igniter so that the plug faces the coil. That will keep you from having to extend that harness.


02-25-2011, 11:57 PM
Awesome I am getting a 3sgte in my gts and now i know what to do when i get my swap.. gotta love this forum

02-26-2011, 06:57 AM
is there any way i could put the harness through the hole where the shifter cables are and not extend anything, i just dont wanna make a mistake by cuting into the wire. ohh yeah before i forget, is it hard to connect the gas line to the fuel rail? is it a direct fit or do i need to use the gas line off the all trac front clip? also does the throttle cable reach with out making any adjustments? thanks guys

02-26-2011, 01:22 PM
You will have to extend the afm harness. There's no way around it. It's only 4 wires. The fuel line will bolt up and the speedo cable will work just fine.

02-27-2011, 02:45 AM
I elongated my harness 30 inches and it reached perfectly running over and behind the intake to the pass hole. An electrician I know gave me some length of sheilded quad wire that can probly only be had through electrical supply co. And I scammed some sheiled dual wire from an ST at the junk yard. That took care of all the sheilded wires. I was going to cut a hole but didnt look like there was room on the firewall anywhere, wish I had checked the trans cable hole, dont know if it woulda fit there cause I didnt look but if others have done that then probly does. I had never soldered a thing in my life before that and it worked out ok. I took my time and took me about 2 weeks to do the elongation. ChrisD and others here helped me out immensly with the trouble shooting. I actually have tons of pics and video of the project but I have yet to cut my movie into sections so I can post it on youtube. There are a couple wiring pics and a comically crappy diagram on my celica page here www.fargosucks.com