What is causing my Z to run rich? So i replaced the mass air flow sensor thinking I would pass emissions and my car is still using to much fuel. I got a code for the part 23710-CD101 wich is the ecm but do you think the knock sensor causes the car to run rich? I thought i might need a new engine control module (ECM) because I already had replace the body control module (BCM). Then i was thinking Maybe its not the ECM, it might be the ECM relay because i saw a crack on it, look at the diagram and then mine.

I found out my car was in a flood 2 months after ownership, it was flooded years ago before I owned but has always worked perfect since I've had it. I've always wanted a 350z since I was a kid and this one is pretty clean and has decently low miles so I'm going to stick with it. I just really need some help, none of my mechanics can find anything that is causing me to fail emissions.

 

I would be a little more systematic on why you failed emissions from the states persepctive - what did the states report say? what did you fail exactly per the states report?

Im sure the knock sensor could cause a rich condition if certain parameters were met but that seems highly unlikey.

In the mean time with the known history of the car I would do a compression test and a leakdown test to ensure the cylinders / rings / valves are healthy -

 

Other's have changed the sub harness to fix the issue

 

bad O2 sensors also give you spurious results. And they could have corroded from water in the exhaust pipes. I would replace all four of them. Even if the car doesn't need them new sensors are a good idea in a flood title. O2 sensors, camshaft position sensors, crank position sensor, and you already replaced the MAF.