Im getting code 43 in my 89 si with a b20b , Im getting a slight miss- bad fuel smell from the exhaust, And awful gas mpg, Can 02 sensor cause this? Also I have a magnaflow high flow cat. Could it be clogged? its only 2000 miles old. I know my tune is good, Im lost and dont wanna just go dumping money into it. Any ideas?

 

Yes - an O2 sensor can have something to do with a code 43. The only thing is, the smell you describe is more in lines with a clogged/failing catalytic converter. It would be a simple to pull down the exhaust and look at it. You could also temperarily run open downpipe and see if the miss/stumble goes away.

 

Dealing with code 43 as well with the recent b16 obd1 converted. Just changed the O2 sensor with Denso brand and the code wouldn't go away. In the process of checking ECU and O2 wires.
Been getting 200 miles to a tank.

 

it's funny because as soon as I put the exhaust and cat on ( I was running open header before ) It was fine, no more than a week later is when it started acting up. Could that cat of went bad that quick? It was brand new. I do hear some rattling under the car near the cat now, which was not there before.

Same here man, about 200- to a tank, its awful

 

Cars are interesting things... yes it could have went bad that fast... Very high possibility you are running too lean on your tune. Rattling (as long as everything is intact and heat shields are solid) typically would indicate the "honeycomb" in the cat has broken apart.

 

Well I guess im gunna pull the cat and see what's going on, It's just clamped on so i wont have any issues getting it off. As far as the code 43 though , the cat wouldnt have caused that though right? My mpg is horrible, The smell of fuel through the exhaust is really bad, the inside of the muffler tip is covered in black soot, plugs are black ( Dry ) the car also dumps smoke out when I step on it pretty hard ( Black )

 

Code 43 can in fact be caused by a bad catalytic converter. Basically code 43 is triggered when the computer can't get the O2 readings within spec by adjusting the timing and fuel. If you are shooting black it would make even more sense the cat is clogged... If you have an exhaust gauge - take out the O2 sensor and put it in - anything over 1psi is typically not good at idle.

 

I will try that also, Im going to try and get the cat off here a day this week and I will get back and let you know how it turned out- Here are the plugs I took out of it today--

 

I had just put those plugs in maybe 800 miles ago.

 

So far code 43 has disappeared for two days...after I traced the O2 wires to ECU and found that the signal and the ground connections were mixed up.
Double check those connections.

 

will do , thanks