Well I've taken my car to e-check twice now and failed both times. The first time I failed CO and NOx which was expected because I still had my gutted cat on, but i figured it was worth a shot. For the 2nd time I put my high-flow cat on and passed CO with flying colors, but still failed NOx miserably. I'm actually double the legal limit. Does anybody have any suggestions of things to check? Last night I checked all my vaccum hoses and my EGR and they all appear to be ok. The EGR diaphragm held vaccum just fine. I've had my car re-programmed by PCMForless, but I don't think there is anything in there that would cause me to fail NOx unless he bumped my timing way up. Could a knock sensor cause this situation since I'm still not using the LT4 knock module? Any suggestions would be greatly appreciated.

 

Injectors could probably use a cleaning, maybe new plugs? Just an idea

 

High NOx can be caused by a lean condition. Also by excessive combustion chamber temperatures... e.g. high coolant temp could contribute.

 

Would my 160-stat have anything to do with it. In my opinion it would make the engine cooler, but what do you think?

 

Can't see how a 160* 'stat would contribute to the NOx problem. It should produce lower coolant temps if you have the fans reprogrammed.

 

Gutted cats, your not ganna pass obviously. High Flow Cats, I'd be worried about it. My buddy did the same thing you did by trying to pass smog with his T/A on HighFlow's and he didn't pass. That's why I didn't get HighFlow Cats and kept my alone. He put in the original Cats and "walla" passed.
In my opinion bro...if your car is for the street just leave the Cats alone, seriously. No Cats stinks, your factory Cats are expensive to tamper with and you can't pass without them. If your ganna swap the Y-pipe, atleast put the factory one back in when you smog it.

 

Give it a little drive before e-test i failed and then did that and what do you know i passed.

 

Plugs and EGR are the easiest possible causes to start with.

 

I live about 20 minutes from e-check and it's mainly highway driving so I got on it a bit to clean it out. I checked the EGR the other day and it appears to be fine. I recently changed my plugs out when I did my headers. I probably have about 3K miles on the new plugs. I'm going to try putting my stock tune back into the car and see if that allows me to pass. I'm still curious about the knock sensor though. I wonder if I put in LT4 knock module if it would make a difference. E-check is horrible

 

I failed 2 years ago because of high NOX which wasn't that high.

I checked it against the previous test 2 years before,and they had tightened the requirements.

So F#@$ them
I had a friend put me through under "modified engine change"