ST185 swap fuel/air ratio, Getting black smoke from my exhaust Options

[ManpreetS512]

Hey 6GC Members,

I hope you all are doing well.

My name is Manu and I am new to this site, so I apologize if this has been discussed else where and I couldn't find it. If there is already a thread, please point me to it and i'll look it over.

I have a 97 Celica GT with a JDM ST185 swap with JDM ECU. The engine is stock with no modifications thus far. This car was given to me as it sat in a garage for 10 years without ever running. Needless to say, I've gone through a lot of different issues starting with replacing fuel lines, gas tank, fuel pump, cold start injector, etc. to get the motor to crank up again.

The car did not have an exhaust since the previous owner didn't purchase one and mainly wanted to get the swap to run. When we got the motor to crank (finally), it was running really rich. So I took it to a muffler shop and had them add a catback exhaust from the downpipe back with turbo muffler and all 2.5" piping.

Now the car has black smoke coming from the exhaust when it cranks up, so I am assuming that the engine is still getting too much fuel. So friends of mine recommended that I may need a ECU tune but in order to do that I would have to purchase an expensive standalone ECU and then take it to a certified shop and have them tune it.

Before going down that route I wanted to post here to see if anyone has seen similar issues with their swap or this engine in particular? I was also wondering if anyone here knows if the O2 sensor on the downpipe is needed for the ECU to function properly? I ask because when the car was at the muffler shop, I saw the O2 sensor on the downpipe and it was not only rusted but the wire connected to it had been snipped clean - so that O2 sensor in not connected to the wiring harness at all. I also get no check engine light which is odd.

I'm thinking that the O2 sensor on the downpipe does need connection to wiring harness and someone may have snipped it to get the car running before since it had no exhaust. I am not an expert by any means and am learning as I go.

Please let me know if anyone can provide any advice.

Thanks,


Manu

[ManpreetS512]

Innovate SCG-1 is one I've been looking at myself. There are competing offers from other makers as well I'm sure, but Innovate guys seem to be near the top right now from what I've read.
https://www.innovatemotorsports.com/products/scg1.php

The thing also has an analog out to feed back to the stock computer in lieu of the stock O2 sensor, but I don't know how easy it is in practice to emulate an output the stock ECU will be happy with.
I know that there was also an offering from AEM at the time Gen2 3SGTE was in it's prime that was pre-programmed to feed the "correct" signal out to the stock ECU, but I doubt there is a solution that does that AND has EBC functionality.

Thank you for this recommendation. I'll look into this as well and see what AEM options are too.

that wideband may have been used to plug up a temporary hole or it was used at some point in its life. Not entirely necessary for your application at the moment unless you go standalone to delete the factory narrowband o2 sensor to run strictly off of the aftermarket wide band.

Do you have the factory o2 sensor in place? If you don't have one, wire one in. They're usually a 3-pin or a 4-pin connector depending on how the harness was done.

Also see if you can borrow another AFM and test that as well to see if it's faulty.

Occasionally, you'll get codes hiding even when the CEL isn't on.

I do have the factory o2 in place but it is a single wire. Located on the top portion of the downpipe. It's in the pictures that I shared - viewable from the engine bay.

I don't know anyone with an MR2 or Celica with this AFM in order to test (I live in Holly Springs, NC). Toyota doesn't make new or remanned ones any more so I would have to buy from eBay and test but not sure how reliable it will be since people just sell used units with no return.