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90 st185 ecu wiring

PostPosted: Tue May 31, 2016 2:45 am
by clayton351
Ok, I bought a car and it came with a lot of receipts but some of them are either bogus ore the previous owner got screwed over by at least one shop.

So I'm trying to get the car to a known condition. It runs pretty good but I'm noticing some stuff is inaccurate. As best I can tell it currently has the following setup.

Sw20 power fc so that should be a Gen 3 setup
Stock harness has been modded to the ecu (might not be exactly correct)
To run properly that would need either a Gen 3 map or apexi map and a Gen 3 ignitor.
I seem to have both the stock gen 2 map and ignitor ( one of the receipts is for an apexi map)
It has an iat sensor on a 2 ft long hose off the back of the plenum that always reads 20 celsius, I have tried a gm iat with the same results.
The car shuts off roughly 1k rpm below where the limiter is set, I believe this is due to the Gen 2 ignitor.
The ecu read out for boost reads higher than my boost gauge, I believe this is because of the Gen 2 map

I have access to a jdm sw20 gen 2 ecu that I would like to run but need to get the harness to a known state to get it right. Does anyone have a diagram that shows wire color at the ecu plugs? Also open to other ideas that don't involve me spending $3-400 on sensors that may or may not solve the issue.

Re: 90 st185 ecu wiring

PostPosted: Sat Jun 04, 2016 12:01 am
by Nitro_Alltrac
I converted my car to 3rd gen electronics last year and it runs well.

You are right about the ignitor, 3rd gen uses a different one from the 2nd gen. The good news is that it uses the same one as a lot of the 5S engines. I pulled the one I used from a GT. I'll look and get the number/code off of the top of the ignitor.

You are also correct about the MAP sensor. I'm kind of surprised it will even run with the 2nd gen MAP. The voltage outputs are radically different between the 2nd and 3 gen sensors.

It is debated on MR2OC as to whether the IAT is even needed. Used one, put it I the intake and used the air meter wiring to get the signal to the ECU. I would move it. I don't know that it will make a difference but it couldn't hurt.

If I were you and the car is currently running, I would get the right ignitor, when you can get from a salvage yard cheap, move the IAT and get a 3rd (or 4th gen) MAP sensor. (4th gen MAP supposedly has the same voltage curve as the 3rd gen but the housing is different). Going back to 2 gen electronics is going to cost you a bit as well. You're looking at a 2 gen ECU and you'll have to have the air meter as well. It sounds like you are too far off right now.

Here's link to some of what I did on my conversion. ... highlight=

Re: 90 st185 ecu wiring

PostPosted: Sat Jun 04, 2016 12:33 am
by clayton351
Gen 3 ignitor came in today, but I'm out of town. I have a Gen 2 ecu and the afm, I would just need to put the wiring back to stock. The shop that did the work (before I got the car) is obviously shady, and I don't trust that they repinned it properly. My tuner says he can make it work by reprogramming for the gen2 map. I'm working on sorting a couple of other things before I take it to be tuned