My car failed the NO part of the smog inspection horribly. What should I look into to fix the problem?

 

nox look it up

 

When you went to the smog shop how long were you driving the car around beforehand?
When you arrived at the shop how long did you have to wait before the test? - did you leave the car idling or did you turn it off?

With numbers that high it's most likely that your catalytic converter is bad OR it wasn't heated up properly when you tested.
If you have replaced the cat - what brand did you replace it with?

 

Yup could be a falty/bad cat...........and ^^^^^^ yeahexplain what he asked tooooooooooo

 

i failed the same thing last year and it was a bad cat...it could also be a faulty o2 but the cat is the best culprit...!!!

 

if he has no cat how much would it give?

 

NOx emissions are the result of high combustion temps.

The EGR valve (if the car has one) is intended to lower combustion temps, reducing NOx. If the car has one, verify that it operates correctly.

Otherwise, a modern cat breaks down NOx in the first stage. That portion of the cat can go without the rest, so NOx can go up without the OBD2 computer knowing, since it only detects O2 (which won't apply to a Civic this old).

Timing advanced too far can also increase NOx, as can carbon deposits on the valves.

If its only NOx that is causing the failure, just dump a bottle of ISO Heet into the tank and go test again. It will lower temps, dropping NOx counts.

And, um, is it just me, or does the picture show 126 PPM NOx measured out of a maximum 828 PPM allowed?

 

I also failed so I replaced the o2 sensor....the cat.....and also the muffler...........my nox wasway high too so it could be a # of things

 

O2 would likely throw off other test readings as well.

To see if your cat is working, drive it around 10+ miles so the cat is nice and toasty (perferably do this on a warm day).
Go to a muffler shop and have them check the cat - they put it on a lift and then use a point and shoot thermometer to check the front and the back of the cat. The readings should be something like a hundred degrees F difference.

 

i just noticed that also and i think the op is pulling our legs or that computer software pulled a typo...!!!

 

No I actually circled over the 1 in the pic.. lol. I didn't notice until you said so, but the reading for the acceleration is at 1126. I will check the cat and the timing. As far as the EGR, I pulled it off a 89 civic I believe. How do I go about cleaning it, checking it's function? I cleaned the bottom portion of it with a brush but that's as far as I went with it.

When I had a hand vacuum pump I tested if it held vacuum and it passed. The car ran rough but did not die when applying vacuum btw.

And also, the car wasn't run for long prior to smog. Probably 5-15 min then tested.

 

I cleaned the egr and the passage (not much I could clean as far as passage..) as good as I could, and ran some iso heet. The 15mph results yielded 50 less NOx ppm (811, 889 is max) but the 25mph acceleration yielded 1 less NOx ppm (LOL)(1125, 828 is max) since the first pre-smog.

I'm going to get the timing checked either today or tomorrow.. but I just tested the cat. Results were exit port of the cat was 10-15 degrees cooler then the intake port. Bad cat?

 

Outlet should be 30~100 degrees Fahrenheit hotter.
100 degrees is rule of thumb, but if your engine is running very clean it won't be as hot.

Do you remember how hot it was reading at?
Cats work at about 500~1600 F.

 

Retard your timing. You get NOx from detonating, whether or not you can "hear" it.

"New cat" is a bandaid...

 

No he didn't tell me the temp. I'll ask if he remembers the temperature. All he told me was that the exhaust was coming into the cat and going out 10-15 degrees cooler.


I'll check it out either today or tomorrow, and adjust accordingly.

 

had the same problem as you did 2 months ago, i put a new cat and bam it passed with no problem

 

So you are saying that if your 15+ year old car is failing emissions then you should retard your timing because replacing your stock factory cat is just a bandaid? How is retarding timing going to make a dead cat come back to life?
Detonation is NOT the only way to get high NoX readings.

He should CHECK his timing and adjust if necessary, but just retarding it is a BAD idea.
Running too lean OR too rich are both bad for a cat.

 

Just to put in my two cents...

I put in these numbers into a lambda calculator and at 25mph the A/F ratio is 15.05 which is on the lean side. OK just barely.

Timing can affect your numbers however you are limited to 2 degrees + or - spec.

Advanced timing can create more compression/Nox because the spark is igniting the gas before TDC.

So if the timing is already advanced, retarding it would lower Nox some. Note the timing is not listed on the report so we just do not know where it is.

The cat is not dead, just dying is all. Going by the left over O2 in the exhaust.

Tell us more about the car, Has it ben driven alot or has it been sitting for a few month's?
The cat will oxidize just like any other metal and make the cat less efficient.
So if the car has been parked I would drive it on the highway for an hour or so. This will burn out the oxidation.

If you have blown the headgasket, coolant will contaminate the cat also.

 

True, but retarding your timing is infinitely cheaper than replacing your cat. And cats, FYI, are not wear items, unless your tune's ****ed up, so the age is irrelevant. What's more likely is he has a shitload of carbon buildup on the pistons and head and some hotspots from carbon crap in there causing detonation... but sure, the cat MIGHT be bad.

I prefer trying all the free methods of passing retarded inspections before spending money, myself. But if you like spending money and possibly not fixing the problem, go right ahead, it's your dollar.

thesmogman, do you actually check that the timing at the crank is +/- 2 degs? I personally retard the hell out of the timing during the driving test on the Ostrich and let 'er rip at about 16:1 afr... pull the a/f to about 17.5:1 and advance the heck out of the timing at idle since around here they don't check NOx except during the driving test... and then upload the old tune as soon as I get the pass.

I've had boatloads of experience in this realm, but that's all for Canadian emissions testing purposes so... do whatever you guys like, just throwing in my 2 cents

 

Sweet. Lots of good info in these replies.

I drove the car for about 1 1/2 hr before getting the second pre-smog done. I beat on it the last hour to get the temps up. Other then that I've been driving it around for a month. Before that I think it was sitting for awhile.

I ran some chemical that's supposed to clean out the whole system (injectors, fuel lines, combustion chamber). I forget the name, but i threw a bottle in the tank. And did a full tune up.

That's about it. I didn't have time today to check the timing but I'll do that tomorrow for sure... and report back with results.

As far as I know the headgasket is good.

 

Yes I do. It is required if the timing is adjustable. That includes jumpering the connector and such. It is a requirement by the BAR. If there is not a spec as in + or - 2 the rule is 3 degrees.

Tuning is not allowed. However we are not required to check the ECU.

 

What exactly do you mean by jumping the connector? A friend told me I need to do something like that while checking timing but he wasn't completely sure.


Also... my cat is bad. Need to replace it ASAP. Deadline is coming up.. so any suggestions on a new cat with a decent price? NEEDS TO BE CALI LEGAL. I would buy OEM but it's $400+ and my budget is tight right now.. I can spend about $100sh or hopefully less but still pass smog.

What about this one?

http://thmotorsports.com/magnaflow/m...=53004-90-1990

 

bump for help..