Help passing Emissions :(
03-31-15, 11:40 AM
#1
Help passing Emissions :(
Sc300 na auto
02 sensors are all newish and magnaflow universal cats newish also. Timing 14* advanced. No vacuum leaks that I can find, no current exhaust leaks. I failed by such a small amount I am not ready to rip the magnaflows out at this point. Running 91 octane, no over heating issues or any drivability problems.
I took it in for emissions first of the month.
Results / Standards
HC: 0.79 / .8
CO: 2.65 / 12.0
NOX: 4.61 / 2.0
Found a big exhaust leak at the manifold to downpipe, fixed that and failed again
HC: 0.45 / .8
CO: 4.59 / 12.0
NOX: 2.06 / 2.0
Failed by .06 on NOX, ugh!
A friend suggested retarding the timing a lot and try again. I dropped the timing back to about 6-8*.
HC: 1.01 / .8
CO: 3.55 / 12.0
NOX: 3.41 / 2.0
Now, should I step the timing back to the stock 10* and try again, advance it a little above 14*? It seems I was so close with it at 14* its so irritating. I've already spent more in emissions testing fees than the registration costs me.
02 sensors are all newish and magnaflow universal cats newish also. Timing 14* advanced. No vacuum leaks that I can find, no current exhaust leaks. I failed by such a small amount I am not ready to rip the magnaflows out at this point. Running 91 octane, no over heating issues or any drivability problems.
I took it in for emissions first of the month.
Results / Standards
HC: 0.79 / .8
CO: 2.65 / 12.0
NOX: 4.61 / 2.0
Found a big exhaust leak at the manifold to downpipe, fixed that and failed again
HC: 0.45 / .8
CO: 4.59 / 12.0
NOX: 2.06 / 2.0
Failed by .06 on NOX, ugh!
A friend suggested retarding the timing a lot and try again. I dropped the timing back to about 6-8*.
HC: 1.01 / .8
CO: 3.55 / 12.0
NOX: 3.41 / 2.0
Now, should I step the timing back to the stock 10* and try again, advance it a little above 14*? It seems I was so close with it at 14* its so irritating. I've already spent more in emissions testing fees than the registration costs me.
03-31-15, 02:19 PM
#5
you did not fail by a small amount. when everything is working properly the numbers should be a fraction of the limits on a un-modified SC300 or 400.
how many magnaflow cats you have on there, 2? that should be enough.
your HC is high which indicates you have unburnt fuel.
your NOX is high which indicates your cylinder temps are way hotter than normal, and is normally a sign that the engine is running lean or there is too much timing advance.
setting the timing high and failing on nox didn;t tell us much, nor did setting the timing low and failing HC (lower timing means less fuel burnt as well) cause you still failed nox so lowering the timing did not fix what I am going to say is the "problem".
stock timing advance is 10 degrees and you should set it there and then figure out why your nox is so high, unless you want to keep on taking e-tests all the time.
changing your timing more than 2 degrees from the base is just as cheating as it is to put in denatured alcohol or e85 which primarily helps with high HC numbers.
normally high nox and high HC don't go hand in hand together cause the unburnt fuel will cool things down and lower nox.
almost seems like you have a mechanical problem like a bad injector or bad plug that is allowing unburnt fuel to pass through to the exhaust, and the o2 sensor is picking it up and leaning all the other cylinders out. something whacky like that is going on if its a stock car, because those nox levels are off the chart. if you do not solve the problem, the motor will not last as long and eventually you will really notice the problem.
how many magnaflow cats you have on there, 2? that should be enough.
your HC is high which indicates you have unburnt fuel.
your NOX is high which indicates your cylinder temps are way hotter than normal, and is normally a sign that the engine is running lean or there is too much timing advance.
setting the timing high and failing on nox didn;t tell us much, nor did setting the timing low and failing HC (lower timing means less fuel burnt as well) cause you still failed nox so lowering the timing did not fix what I am going to say is the "problem".
stock timing advance is 10 degrees and you should set it there and then figure out why your nox is so high, unless you want to keep on taking e-tests all the time.
changing your timing more than 2 degrees from the base is just as cheating as it is to put in denatured alcohol or e85 which primarily helps with high HC numbers.
normally high nox and high HC don't go hand in hand together cause the unburnt fuel will cool things down and lower nox.
almost seems like you have a mechanical problem like a bad injector or bad plug that is allowing unburnt fuel to pass through to the exhaust, and the o2 sensor is picking it up and leaning all the other cylinders out. something whacky like that is going on if its a stock car, because those nox levels are off the chart. if you do not solve the problem, the motor will not last as long and eventually you will really notice the problem.
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