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

[slavie]

You have an OBD1 system and I don't know whether it has closed loop monitoring (the one where you rely on fuel trims off O2 sensor), but I'd save reconnect the upstream o2 sensor, the one in the DP before any catalytic converters.

2.5 exhaust is plenty for a stock engine. Definitely not an issue in your case.

Check fuel pressure to make sure the FPR is working. If the pressure is too high, it will be dumping too much fuel in. Also make sure the reference vacuum lines are connected to the FPR.
You may be dealing with leaky injectors if they sat with bad gas for 10 years. May be time to have them cleaned.

Finally, are you sure the smoke is black and not blue-ish as in burning oil?

[ManpreetS512]

You have an OBD1 system and I don't know whether it has closed loop monitoring (the one where you rely on fuel trims off O2 sensor), but I'd save reconnect the upstream o2 sensor, the one in the DP before any catalytic converters.

2.5 exhaust is plenty for a stock engine. Definitely not an issue in your case.

Check fuel pressure to make sure the FPR is working. If the pressure is too high, it will be dumping too much fuel in. Also make sure the reference vacuum lines are connected to the FPR.
You may be dealing with leaky injectors if they sat with bad gas for 10 years. May be time to have them cleaned.

Finally, are you sure the smoke is black and not blue-ish as in burning oil?

You are correct, it is OBD1 system. The O2 sensor before the CAT is connected. Also, the muffler shop was *slightly* mistaken. They did not test drive the car and told me that when they first installed the exhaust they saw a puff of black smoke but did not pay attention to if it was consistent or not. They then cranked it back up to park it. When I went to check the car myself, there was absolutely no black smoke at all. There was some blue-ish smoke if I hit the throttle but that could be because there is no cat. So I think the fuel problem is good.

The problem now is that the car has trouble going over 3000 rpm. It idles fine (around 1000 - 1100 rpm) and sometimes in first I can get it up to 4000 rpm but when I am drive it gives a slight shake around 3000 rpm and does not let me pass it. I did reset the ECU and when I did that, I think the cylinder flooded. I say this because it was cranking fine and once the ECU reset it would not crank anymore (battery was fine). The next day, it cranked and started up right away but still had the same problem (I think the extra fuel evaporated).

I was looking online and I found a few things that mentioned this issue could relate to timing. I don't have the proper tools to check the degree but I read that it should be at 10 degrees when the spark plugs ignite. It does sound like it is misfiring when I get it up to 3000 rpms though. One of the problems I have is there are no gauges for fuel pressure or air/fuel mix so it is hard to isolate where the issue is.

Does anyone have any suggestions for this or have ran into this issue?