I have a 99 EK with a SOHC ZC engine. The catalytic converter and O2 sensor are not OEM and about 2 years old. Everything else is stock.

Any ideas what could be causing these results?

Thanks

 

need more info!

 

Like what?

 

Is your engine light on? If not O2 sensors should be working and it may be the cat again. Try using a bi-directional scan tool to check the real time voltages to the two O2 sensors. Make sure your car is warmed up and check the voltages. O2 sensor #1 (upstream/before cat) voltage should bounce around. O2 sensor #2 (downstream/after cat) should hold steady at 0.5ish volts. If #2 is bouncing around, it would indicate a bad cat.

 

No, the check engine light is off. I was looking at those voltages the other day but had no idea what they were supposed to be. Thanks, I'll check them again.

 

I would do as Steve said and check the voltage of the O2 sensors. I have had trouble getting aftermarket/high flow cat's to pass emissions in the past. Numbers that high typically indicate a bad cat though.

Not sure how close to Murrieta you are, but I have some spare OEM O2 sensors from a 99 D16Y7 that I keep as back up's just in case, you are more than welcome to borrow one or both if you need.

 

Is it a real catalytic converter or one of those Ebay test pipes (aka hi flow cats)?