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I think i may have an exhuast leak at the front O2 sensor that is causing me to fail my NOx emissions test. here are the pics (sorry best i could do right now while the engine is HOT):








is that an opening that needs to be fixed???

AJ

i was able to fit a small allen wrench down the side where the hole is, but when i turned the car on and increased the rpms, i couldnt feel any suction..????????

any thoughts???

if it were leaking you would see black carbon biuld up coming out of the hole
looks like a crappy weld tho and could use a touch up

and it would take a large leak to fool the o2 sensor to lean the engine out enuph to fail nox you would hear it
the leak would have to be large enuph to let plenty of atosmosphere in the exhaust so the o2 sensor would see exta o2 and tell the ecm the engine is running rich a pin hole would only push exhaust out and would not suck o2 in

i would look else ware like dirty injectors bad temp sensor slow o2 sensors
weak catalyst excessive carbon biuld up inside combustion chamber all these things can cause high nox
but there is so much more that could also cause it
a new cat can cover up lots of probs but the cat wont live long if you dont find the root problem

max kl wrote: a pin hole would only push exhaust out and would not suck o2 in

Not necessarily the exhaust gases at this point of the exhaust is still travelling at high velocity. Depending on the where the hole is the in relation to the tip of the sensor or welding slag inside the pipe the high velocity gas flow will create a vacuum through the hole if anything rather that blow out through from it.

However I would have to agree with you that the problem is some where else. High NOx results usually means high combustion temps not a run rich condition. If it were rich you would see a high CO and lower NOx condition. If anything the engine is running lean which would elevate the combustion temp if not this then the catalytic converter is defective.

I dont know if it's me or something. but where in the picture do you see a hole in the pipe. Doyou mean the silver thing around the O2 bunge, where O2 screws in.

If it's the thing your talking about, than its the heat shield and underneath that is a insulation around the pipe. The actual exhaust pipe is underneath two layers. It's that brown/rust looking color thing.

And about NOx isnt EGR responsible for the NOx, it could be a bad EGR (Exhaust Gas Recirculation), helps reduce emissions, I think you should check that too, EGR Valve could be bad.

I could be wrong, but thats just my two cents.

Good Luck hope you pass emissions, because they suck, I hate emissions.

THANKS

other than running lean, what causes high comb. temps?

If i switch my k8 ecu back in there i will run rich right? that should bring the nox levels down. But will i fail the CO and HC tests?

Also i am using 91 octane gas, if i switched to 87 or 89 would that retard my timing enough to help me pass any of the tests??

emissons rock i love being able to change the gasses around its like tuning for more power well i enjoy it and maken money do in it is a plus


anywaz
excessive igniton timing will cause high comusution chamber temps but you realy cant adjust that the ecm will use the crank sensor to adjust it where it wants the timing to be but changing ecms may help an ecm with less agressive timing curves would help

tb boot leaks carbon biuld up on pistons maf probs can cause high nox

but others on this forum seem to pass with a good cat alone

one thing i have always wanted to try is running the dyno test with the [ten] jummperd to ground so the ecm cant control the timing and see if you can get the timing where nox and hc are low