I failed emissions the first time, so that gave me the green light to get some aftermarket parts[8D]. I bought new intake, headers, catalytic converter, and catback exhaust. Went back to the MVI with confidence, only to fail again. The problem is with my NOx production. I'm double the standard. The standard is suppose to be 1259 and i'm producing 2299 ppm. I thought it might be my O2 sensor since i am using the original, but i checked it with my multimeter and the voltage cycled like it was suppose to after about 2min warm up between .1 and .8 volts.

So, now i'm thinking it could be my TPS, since i have noticed, even beforei installed all those new components that my gas mileage has dropped. I used to be able to do about 315mpg on a full tank and still have .5-.6 gallons left, to now i'm struggling to get 275-285 on a full tank. The only problem is when i checked the sensor, the voltage was where it is suppose to be, 5 volts. But i do have to by a probe for my multimeter to see the readings when i open the throttle. I also checked my MAP sensor, and the reference was dead on 5 volts, but the signal voltage was 4.67 volts, curious if that has any revelance to my situation.

Oh and my carbon dioxide, hydrocarbons, and oxygen production are all well under standard on my report.

Though i have noticed some nasty rot in my radiator, i have a JVT 3layer radiator coming in, so i'll replace that soon, i read on a website that a malfunctioning radiator can also effect my NOx production, but the only thing is that my engine never runs hot. It never reaches midway on my temp gauge.

I really need some help guys, i hate having that rejection sticker on my windshield.

Thanks in advanced.

 

Running too lean can cause the problem, though you have already checked the O2 sensor.

Also check that the ignition timing is set to spec and that the coolant temperature sensor is working properly.

 

check all of the connections in your exhaust system. if you have any leaks, especially in the header before the O2 sensor, it will throw off the o2 sensor enough that it can lean it out and make NOX go through the roof. also, too much carbon in the cylinders will cause nox to spike. Seafoam seems to be the running theme here for reducing carbon. give that a shot too.

 

sea foam you say, i'll try that, can i get that at autozone? Also i did notice some oil/carbon buildup on my v-tech solenoid when i replaced the o-ring. But also, what would decrease my mpg so much. it's been happening for a while, even before i replaced those parts?

 

Wouldn't an exhaust leak before the O2 sensor cause the engine to run rich? My understanding (possibly too limited) is that an exhaust leak in the header would elevate O2 level readings by the O2 sensor, and then the ECU would compensate by increasing the amount of fuel to the cylinder.

 

yeah, but it also screws with the cat. and i think the real problem is the temperature of the air. the cold air seems to throw off the o2 sensor. I saw this same problem on my brothers wifes hatch. the NOX were too high, and we hunted around for a cause for days, then noticed a little puff of smoke come from the header and we found a hairline crack in the stock manifold. once we fixed that, it passed fine.

 

well the headers are brand new, they are 4:1 Ceramic Coated DC Headers, but i am using the original gaskets....

 

maybe try the seafoam first, then if it still fails, replace the gaskets.

 

yeah, i just bought 2 16oz containers. I put about 4 1/2oz in the oil, and 12oz in the fuel tank. Next is for the manifold. after that i'll take it to the MVI, bright and early tomorrow.

Curious, whic vacuum line is best to use. I have the d16z6 motor. I know i have a vacuum line straight to the head, and one above the throttle body. Is it best to use the one above the throttle body?

 

run some through each. that way you get it spread through all four cylinders more evenly.