Helpéadvice on helping my Miata pass failed emissions
#1
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Join Date: Sep 2005
Location: The Golden Triangle, Ontario
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Helpéadvice on helping my Miata pass failed emissions
Hey guys,
My wife's 90 with ~298000kms just failed emissions today.
I am looking for some tips to help pass.
I can probably grab a good used Cat from work to help pass but I am hoping to just tweek a few things to pass...
curb idle test
limit / reading
hc 200 81 pass
co 1.00 0.15 pass
no n/a n/a pass
speed test
limit / reading
hc 78 83 FAIL
co 0.44 0.30 pass
no 907 798 pass
What do you guys suggest to help pass the HC test?
Thanks for the help!
My wife's 90 with ~298000kms just failed emissions today.
I am looking for some tips to help pass.
I can probably grab a good used Cat from work to help pass but I am hoping to just tweek a few things to pass...
curb idle test
limit / reading
hc 200 81 pass
co 1.00 0.15 pass
no n/a n/a pass
speed test
limit / reading
hc 78 83 FAIL
co 0.44 0.30 pass
no 907 798 pass
What do you guys suggest to help pass the HC test?
Thanks for the help!
#2
Boost Pope
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Join Date: Sep 2005
Location: Chicago. (The less-murder part.)
Posts: 33,455
Total Cats: 6,874
There's no way to adjust fuel, and from your other readings it's obvious that the O2 sensor is working.
All else being equal, retarding the ignition timing will decrease HC emissions somewhat.
Try dialing it back by 5 degrees (from wherever it is now) at idle with the TEN-GND jumper set. Some experimentation may be necessary, as all else being equal, retarding the spark will decrease HC and NOx, but slightly increase CO.
If you want some in-depth data, here's a good source: http://dspace.mit.edu/bitstream/hand...pdf?sequence=1 (timing vs. HC starts on page 53.)
All else being equal, retarding the ignition timing will decrease HC emissions somewhat.
Try dialing it back by 5 degrees (from wherever it is now) at idle with the TEN-GND jumper set. Some experimentation may be necessary, as all else being equal, retarding the spark will decrease HC and NOx, but slightly increase CO.
If you want some in-depth data, here's a good source: http://dspace.mit.edu/bitstream/hand...pdf?sequence=1 (timing vs. HC starts on page 53.)
#3
Junior Member
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Join Date: Sep 2005
Location: The Golden Triangle, Ontario
Posts: 283
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Thanks for the help Joe,
I think I will retard the timing to 5' and see what happens - i am pretty sure it is set to 10' or 12' now.
I guess I'll also check the air filter and plugs.
I changed the oil last week and have been running high test too.
If it still fails I may reinstall the old exhaust back onto the car which has a newer cat on it.
Thanks.
I think I will retard the timing to 5' and see what happens - i am pretty sure it is set to 10' or 12' now.
I guess I'll also check the air filter and plugs.
I changed the oil last week and have been running high test too.
If it still fails I may reinstall the old exhaust back onto the car which has a newer cat on it.
Thanks.
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