I have a '97 Honda Civic that didn't pass the emissions test. It tested with high NOx at the low speed test. I was wondering what would cause this. I know it has to do with high combustion temps, but what would have turned it around this test and not two years ago. It was at the top of the scale but passed during the higher speed test. The MIL light is not on, and I have not checked any of the O2 sensor outputs to see if they are putting out the right info. BTW the car has 257K miles.

Rod

Running lean can cause higher combustion temp, also excessive carbon build up in the chamber. Have a decarb service done(might help).Timing being off may cause it also.

I'm guessing it needs a new catalytic converter. Has it ever been replaced before?

is there an egr valve on those things?

buy american ;) :D

buy american ;) :D


Its my beater car.... I wouldn't even think about treating my 3 other AMERICAN cars like this... get in it and drive..

With regards to the Cat, I have never put one on it, Ive had it for 4 years and put on close to 100k of the 257K. It does have an EGR. Im going to bring it into school tomorrow and check the EGR function and make sure it isn't carbon fouled, Im going to recheck my timing, its been a couple years now for that, but IIRC I set it at the top end of the spectrum. I will also have the carbon service done.

Thanks Rod

if your NOX is what causing problems ..... run higher test gas it burns slower also figure out where the timing is an set it as far retarded as allowed ....

a new cat might be needed then becouse of the HC's that changing the fuel & timing caused ....

its a balancing act you can NOT change one without effecting the other :(

buy american ;) :D

X2


You could try to steam clean the combustion chambers
introduce a small I mean real small amounts of water into the air stream of the TB.
I use a drink bottle use my thumb over the opening to contol the water flow about 4 oz should do it for a small 6/4 banger

The water becomes steam with combustion pressure and heat.
Oh rev. the motor up to around 3000 rpm induce a small amount of water enough to cause a slow down in rpms work the accelerator just don't stall the engine. Let the engine recover then repeat until you use up the water. After this I normally run Marvel Mystery oil in the gas to lub top end again. Might be a quick fix for your beater

EGR function and make sure it isn't carbon fouled, Im going to recheck my timing,

When I had my honda smogged in CA, they checked the timing.

Check this out on EGR:
http://www.tegger.com/hondafaq/misc/t2t013.pdf

When I had my honda smogged in CA, they checked the timing.



Matt,

They are SUPPOSED to check the timing, I know I advanced it to the top end a year and a half ago, but was planning on retarding it to its lowest allowable limits. They have what is known as the "Smog Check II". They use a Dyno and do a 14-16 mph test and then a 24-26mph test. I passed on the top end but failed the bottom end. The first time I took the test it was aborted because my cooling fan was not working and it over heated. I went home and shorted the fan sensor so it was on all the time, then went back @30 min time period.

When I wathced the second test, I missed the first 5 or so min, and got back there when he was finishing the high speed test when he was then moving on to the gas cap test. My gas cap failed so he pulled out a new one and threw it on the machine to pass that part of the test knowing the low speed probably wasn't going to pass. He told me that if the low speed failed it was a moot point, but that if it all passed he would sell me the new cap.