DTC #72... need some advice

[racin-type]

Just bought this nice 95' 240sx base, stick. idles fine, drives fine with a little stumble on low rpm's but running very rich. at first the check engine light wasn't on then i ran the gas tank low and it popped on. filled up the tank, check engine light went off ok fine. second time pops on again but after filling tank it stayed on.

Check the ecm for the code and its a #72 three way cat function. I'm thinking one or both of my O2 sensors is running a little slow and is throwing of the ecm's fueling cause me to run rich. also i currently have an exhaust leak right where the cat connects to my cat-back exhaust system. is this an issue? in the fsm it says check for leaks upstream of the cat.

will check the O2 voltages at the ecm tom. anyone got any input, would be appreciated. Also I've heard i can just buy universal Bosch O2 sensor and splice it up, is this true? Is the front and rear o2 sensors the same one, so i just buy two or are they different? where is a cheap place to buy these sensors?

thanks Lo

[s13sr20chris]

o2 sensors are good but a three way cat code cannot be caused by a faulty o2 sensor. its a bad cat or possibly that exhaust leak. the easiest fix would be to get a new cat(high flow maybe) and gaskets.

[racin-type]

i'm not disputing you solution, i'm just confused, why would a bad cat cause me to run rich.

can anyone recommend some high flow cats that would let me pass emissions.

Thanks again

Lo

[s13sr20chris]

it wouldnt, that is most likely another problem. i was refering to the dtc 72. running rich is likely a maf/circuit, temp sensor/circuit, etc typ of problem.

[racin-type]

i c, so i should try to fix that problem before changing the cat cause then the replacement cat would eventually fail correct?

If i correct this rich condition, would the DTC 72 code go away or will i still have to change the cat?

Ever had experience with DEC cats? they make a front one for the 95 240sx

Thanks

[s13sr20chris]

no experience with them. i would def fix the cat problem last. figure out why the car is rich. start by checking maf voltage and coolant temp sensor resistance(hot and cold).