I replaced my cats, exhaust system, and cleaned my MAF, but I'm still running rich so I'm still failing smog.

I was told that it's because of the oxygen sensor. So i'm looking for it on the exhaust manifold and can't find it.

Does it not have one? What other reason could it be that i'm running rich?

 

What year?

 

Sorry, It's a '79 zx.

 

What specifically failed? HC's? CO? Nox? And by how much?

A great read on diagnosing 280zx smog failure: https://www.zdriver.com/forums/280zx...houghts-31671/

 

My HC's were measured 130 at 15mph and 74 at 25mph.
My CO was 2.28 at 15mph and 2.11 at 25mph. The max is 1.36 and 1.16.
My NO was 106 at 15mph and 35 at 25mph.

My CO is what caused me to fail. Everything else I am under the maximum allowed.

 

I don't see an O2 sensor on the '79 wiring schematic or in the FSM...

 

What is your timing set at? I don't remember if a '79 has a cylinder head temperature sensor, but it could be that too since yours doesn't have an oxygen sensor. You don't have any vacuum leaks right?

Edit: Also check your catalytic converter too. If it checks out ok, take a long drive on the highway of at least 30 minutes and see if that changes your numbers at all.