Car is a bone stock 95 Acura Integra 4 door LS. This car passed smog 2 yrs ago with flying colors. Had readjusted the valves and re-shoot the timming couple months after the smog test, drove it like that without replacing anything ever since, only oil change every 3-4K miles. Now this car has bout 250+K miles and it eats quite a bit of oil, but does not smoke, pings a little on hard acceleration( might be too advanced when it had the timming re-shoot) but still runs very good.

So recently before this new smog test, I had change the old spark plugs and found out that the tip of the spark tip had kinda melted in a way, not extremely just a bit slanted. It was somewhat getting poor gas mileage on small streets, but if in highway it still gets decent mileage around 350+miles full tank. So I replace the old spark plugs with new ngk platinum ones,(I know I didn't really need to use platinum spark plugs but got it for a good price).

So everything seemed gravy and I took it in for a smog test today, it pass the 25mph test but failed the 15mph test because Nox was high.

here were the results for 15mph test

please note: MAX=Maximum Allowable Emissions / AVE= Average Emission for passing vehicles / MEAS= Amount measured

CO2 MEAS 14.07
--------------------
O2 MEAS 0.16
--------------------
HC (PPM)
MAX 90
AVE 41
MEAS 59
--------------------
CO
MAX 0.54
AVE 0.12
MEAS 0.28
---------------------
NO (PPM)
MAX 711
AVE 150
MEAS 0780
---------------------
Results FAIL


Results for 25mph test

CO2 MEAS 14.09
--------------------
O2 MEAS 0.11
--------------------
HC (PPM)
MAX 43
AVE 25
MEAS 43
--------------------
CO
MAX 0.53
AVE 0.10
MEAS 0.22
---------------------
NO (PPM)
MAX 754
AVE 112
MEAS 0521
---------------------
Results PASS

I did some search online and found that Nox was due to having too much heat in the combustion chamber, causing a lean mixture perhaps. Kinda makes sense to me cause remember my old spark plug tip was melted in a way.
Im kinda comming to the conclusion that it could simply just be that my timming is a little too advanced, but i wanted to post this here to get second opinions on what i could or should check/replace before taking it back in, cause it kinda hurts to give away 42 dollar each time you fail lol.......

 

you can try retarding the timing a little bit,
or if you have programmable ecu, add a wee bit of fuel too.
maybe try stock intake if you have it.

I have hondata, datalogged the etest, and tweaked the tune a little, took 3 tries though.

 

yeah im going to retard it a bit and use a new o2 sensor since i have a brand new o2 laying around. Everything is stock, this car has never been modify, stock at the engine all the way to the tail pipe.

 

Sorry to tell you this but you are running at 14.6 a/f ratio. In other words perfect. Your problem is your cat. On this hondas and acuras without egr valves, your only way of lowering nox is by valve overlap and the cat.

You need a cat.

 

just curious where you find out im running 14.6 a/f ratio? how do i fix this valve overlap? retard the distributor timming?

 

at the top of each test where it says CO2 MEAS is where he found your a/f

 

nah man. co2 is basically an indication of how well the engine is running. You have to use a lambda calculator to find out your a/f ratio. Go to smogsite.com. I have my smog license and work out of a dealership. I deal with this on the daily.

Just helping you out so you don't throw more money away

Valve overlap is basically the valves overlapping their opening and closing to keep temperatures in the combustion chamber down. Dont worry bout it. You only have 3 degrees of timing adjustments legally. Thats not the problem.

 

i appreciate your help bro, so your 100% sure its the cat then?

 

Yes sir. Just to give you a little more info. Co is basically a richness indicator. If you are running rich you will have more. And usually you will have hich HC to along with it. Hc is unburnt fuel. Also you need to watch you o2. You should have close to nothing. If you have too much thats an indication of running lean, or a misfire.

 

do u think that the cat was just not hot enough when they did the test? I only drove for about 5 mins on the freeway and 5 mins on the street then shut it off for about 10 mins before they did the test.

so is my o2 running lean, r do u think my o2 sensor is bad? My buddy has a brand new one that he's welling to loan me.

 

what about carbon build up in the combustion chamber (pinging)?

 

The car just sitting there while they fill out the info on the screen would be enough. And obviously the o2 is working correctly cause your a/f ratio was 14.6. Thats perfect. In a honda you would need a crap load of carbon deposits to cause pinging. At that point you would be having other problems.

 

my turbo h22 took 3 tries to pass,
couple things I did to try and lower emissions:
-was running hot at idle/low speed, so spaced up my hood
-couple coats of high temp ceramic paint from turbo to cat
-heat wrapped turbomanifold/ downpipe/ cat
-put in some coolant additive

20min drive down highway, premium fuel,

try retarding the timing just a little, it does take much to drop nox enough to pass
also heard gasline anti freeze helps, alcohol in it, maybe try some seafoam....

running plugs with the right heat range?

 

not sure what heat range its suppose to be but its the regular one u get from auto part store, its a #5 plug NGK

 

My 94 Civic Ex with about 311k had the same problem with the 15mph test. Got a new o2 sensor and cat and the nox went down from 2629 to 154 after the installation. At the actual smog test it read at 207.

 

replace that 15 year old Oxygen sensor and reset pcm.

 

Retard the dizzy a bit and re-test. Ill give you my car if you fail. lol

 

change the cat and pass like nothing, the cat drop the nox down from 700+ to like 30

 

Take the test on gas + E85?

 

cool. good thing. Hey mike lowwrry. Sign over that pinkslip

 

lol didnt see that but im sure he wont, i didnt touch the timming watsoever, just new cat and re-test pass!!!!