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Car Forum / Honda Cars / March 2008smog numbers
my 89 civic just passed smog, but only just - the NO emissions are very high. question from the smog gurus: anything i can do for the old girl, other than replace the catalyst? /is/ it a catalyst problem? 15mph CO2 = 14.7% O2 = 0.6% HC = 31ppm CO = 0.09% NO = 853ppm 25mph CO2 = 14.6% O2 = 0.5% HC = 20ppm CO = 0.08% NO = 788ppm max NO #'s are 859 and 798 respectively. other than that, everything is all factory and adjusted per the honda manual. > my 89 civic just passed smog, but only just - the NO emissions are very > high. question from the smog gurus: [quoted text clipped - 19 lines] > other than that, everything is all factory and adjusted per the honda > manual. jim, don't panic. What are the car's numbers from previous years? I have personally found on /numerous/ occasions with different cars that I/M testing equipment has a tendency to give weirdly skewed results on particular occasions that do not repeat on subsequent testing. If this is out of character for the car, chances are excellent that it's a one-time glitch. If you retest, I'll bet you'll find the numbers go back to what you're used to seeing, with no work having been done at all. Your other numbers are sparkling for an '89. Must be all that maintenance, eh?  SignatureTegger The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ >> my 89 civic just passed smog, but only just - the NO emissions are very >> high. question from the smog gurus: [quoted text clipped - 34 lines] > Your other numbers are sparkling for an '89. Must be all that maintenance, > eh? the previous smog numbers were similar, only just squeaked by on NO, so there's consistency. maybe i should swap in a crappy old set of spark plugs and retard my ignition a touch before my next test - weak combustion would fix the "problem". >>> my 89 civic just passed smog, but only just - the NO emissions are >>> very high. question from the smog gurus: [quoted text clipped - 41 lines] > spark plugs and retard my ignition a touch before my next test - weak > combustion would fix the "problem". Don't they check your timing during CA smog checks? I've been told that every extra one degree in timing advance is worth about 100ppm in NO. If that's true, you could retard it to 14deg BTDC (or your allowable minimum) and you'd be OK for that. Another thing you can try is to make sure the fuel system is full of Sunoco 94 or other heavily-oxygenated fuel. And if it's possible, get tested on a wet, rainy day (yeah, I know this is SoCA...). Ambient moisture may help drive combustion temps down. Have you checked for air leaks into the exhaust before the cat? These will really drive up NO readings. If all the above is tried to no avail, then you probably do need a new cat, as the reduction side has had the biscuit. SignatureTegger The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ >>>> my 89 civic just passed smog, but only just - the NO emissions are >>>> very high. question from the smog gurus: [quoted text clipped - 47 lines] > about 100ppm in NO. If that's true, you could retard it to 14deg BTDC > (or your allowable minimum) and you'd be OK for that. noted. it's dead on right now. > Another thing you can try is to make sure the fuel system is full of > Sunoco 94 or other heavily-oxygenated fuel. And if it's possible, get [quoted text clipped - 3 lines] > Have you checked for air leaks into the exhaust before the cat? These > will really drive up NO readings. all good. > If all the above is tried to no avail, then you probably do need a new > cat, as the reduction side has had the biscuit. that's what i suspect. but i'll plod along until the next time it needs a test. counterintuitive to all this though is that this engine takes a really long time to warm up. new[ish] radiator, new temp sensor, two new thermostats, all new hoses. if the NO levels are high, it implies it's running hot, but the opposite is the case. all very weird. >> If all the above is tried to no avail, then you probably do need a >> new cat, as the reduction side has had the biscuit. [quoted text clipped - 6 lines] > thermostats, all new hoses. if the NO levels are high, it implies > it's running hot, but the opposite is the case. all very weird. Have you inspected your EGR for proper flow? These old cars won't set error codes for insufficient flow. It's my understanding that high NO is unrelated to cooling system temperature; it is solely a function of peak combustion temperatures. It is therefore possible for a car that appears to run cool to have excessive NO. SignatureTegger The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/
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