S13 running rich---Leaking Exhaust Manifold to blame?

[mhosey33]

I have a 92 240sx all stock and I have been having intermittent problems with it running rich and running rough for several months.

It will do it once or twice and then not do it for a couple of weeks, but recently it has been acting up alot more.

Here is what I have done to it, new plugs, wires, cap and rotor button, O2 sensor, tried different MAF sensor and put in new coolant temp. sensor and all of this has not helped.

I took it to my local mechanic and he checked it out and he is pretty much at a loss, he did say that since the exhaust manifold was leaking that it may be messing up the air/fuel ratio in some way, but he was not positive in this.

I am getting ready to take it to the dealership to see if they know what is going on and I was Just wondering if anyone had any suggestions or had encountered this problem before.

Thanks in Advance Guys

[crzycav86]

I'm no mechanic, but if your o2 sensor is seeing fresh air coming in through the exhaust leak, it will add more fuel to try to compensate for this "lean" condition. So the exhaust manifold is a plausible solution.

Your fuel injectors aren't leaking are they?