Failed smog with high HC and CO

[surreybc]

re: 1991 240sx

High HC(489 ppm) and CO(9.99%). Nitrogen Oxide was the best in 5 years.
(similar results on both driving and idle test). They said the CO was the worst they have seen.

I recently installed a new catlytic converter. Had my distributor out and timed it to about 25 before top dead center because it idled better at that position. no check engine codes.

[BigVinnie]

HC's will run high if you advance timing. Timing should only be within 2* plus or minus of 20BTDC for KA24de engines.
For HC's and CO's check your ignition system, O2 sensor, and MAF. O2 sensor will more than likely drop both those CO and HC numbers.
New fuel filter would be good too, hope that helps.

[surreybc]

HC's will run high if you advance timing. Timing should only be within 2* plus or minus of 20BTDC for KA24de engines.
For HC's and CO's check your ignition system, O2 sensor, and MAF. O2 sensor will more than likely drop both those CO and HC numbers.
New fuel filter would be good too, hope that helps.

thanks I will look into that. The ecu ignores the O2 sensor during idle by design so im not sure if it can be O2 sensor since my problem occurs at idle too.

[SoguRacing]

yea, if i were you i would retard you timing back to factory specs. just because a car runs better with it set there doesn't mean it's best for the car... or my lungs.

[gotspins13]

yup^ timing has to be at factory and if you have ac and it was on it advances your timing if its on and will make you fail happaned in my last coupe

[surreybc]

hugggggggbbb

[Hi-PeR]

re: 1991 240sx

High HC(489 ppm) and CO(9.99%). Nitrogen Oxide was the best in 5 years.
(similar results on both driving and idle test). They said the CO was the worst they have seen.

I recently installed a new catlytic converter. Had my distributor out and timed it to about 25 before top dead center because it idled better at that position. no check engine codes.

did u ever find out what caused these problems?? I recently got my smog checked and my car was considered a gross polluter. I also have a 91 240sx.
15 mph HC MAX 118ppm Meas 170ppm C0% MAX 0.75 Meas 0.94
N0 MAX 799ppm Meas 1364
25 mph HC MAX 93ppm Meas 190ppm C0% MAX 0.63 Meas 7.98
N0 MAX 738 Meas 205
I'm thinking it might be a couple of separate issues, my biggest concern is the huge c0 jump at 25 mph. I just recently replaced(just put around 2k mi) the long block(came with new timing chain) and i noticed the engine is a lot louder than before, sounds like the timing chain.. could this be a factor?? The sound has been there since after the install, I just figured it was a loud engine, couldn't feel any effect on performance. Any suggestions are appreciated!! Thanks

[surreybc]

I ha I failed again when I plugged it

[Hi-PeR]

okii thanx, ill tell the shop to check out the o2 sensor and connector!

[240sxxs]

currently i have the same problem but it for SR20....pass the nox but fail HC and CO ....CO need twelve and i put out 34.93 that uber fail.....
lol..will retard the timing affect on the engine performance and perform anyhow ?

[dts13]

if you have that high of CO then ur running waaay to rich. fix that problem then do a pretest to see what you get after.

[240sxxs]

if you have that high of CO then ur running waaay to rich. fix that problem then do a pretest to see what you get after.


well i currently know that..burn fuel like crazy...i notice that...well i currently cant tune the car right now...cause dont have money yet..but as many of you or even heard of Fueled performance in Tempe Arizona...lol..yes that where i will get my car tune and fix all the problem for emission...i talked to the guys..even on the phone he can surely know what is wrong with my cars..i currently dont know what size of in injector im running...but i have 4 brand new sard injector that im thinking will be putting in the car and tune wth my PFC..do u guys think will my car ok .. with 660cc the motor is S14 SR20DET

[Hi-PeR]

i found out the reason for the noise coming from the engine, i need to replace the timing chain tensioner =/ dunno if it will help my emissions any, but at least it will stop that crappy rattle noise at idle

[Veracity84]

did u ever find out what caused these problems?? I recently got my smog checked and my car was considered a gross polluter. I also have a 91 240sx.
15 mph HC MAX 118ppm Meas 170ppm C0% MAX 0.75 Meas 0.94
N0 MAX 799ppm Meas 1364
25 mph HC MAX 93ppm Meas 190ppm C0% MAX 0.63 Meas 7.98
N0 MAX 738 Meas 205
I'm thinking it might be a couple of separate issues, my biggest concern is the huge c0 jump at 25 mph. I just recently replaced(just put around 2k mi) the long block(came with new timing chain) and i noticed the engine is a lot louder than before, sounds like the timing chain.. could this be a factor?? The sound has been there since after the install, I just figured it was a loud engine, couldn't feel any effect on performance. Any suggestions are appreciated!! Thanks

Most of the time it is not your CAT. Amazingly my best friend/ smog guy educated me a lot about smog.

Our cars s13 (ka24de) timing is idealy, 20* BTDC +/- 2*degrees.
Okay:

1. You must retard your car in order to give it a better chance of smogging. 17-19 degrees is fine.

2. It also depends on other factors:

2a. Car must be driven for a while so that the CAT warms up
2b. A gigantic fan must be put in front of our cars to get cooler air
2c. Your technician should REV the car in order to warm up the cat
2ca. When you turn off your car, the cat cools down very fast and without proper warming up of the CAT you will mostly fail.
2cb. Impoper gear change at improper RPM may be a factor as well.
IE:

I failed: 15mph at 1,100 rpm (shifted from 1st gear to 2nd)
NOX measured: 1083 / Max: 780

I passed: 15mph at 2,900 rpm (shifted from 1st gear to 2nd)
NOX measured: 81 Max:780

Same day! I didn't do anything but take it to my Smart and brilliant friend.

WOW! WTF? just for shifting right???

Why?

Well, vaccume. My friend said the idiot who tested my car originally couldn't drive for shit and was too lazy. At higher rpm there is more vaccume to open any EGR related vacumes, on old cars like S13's it is ideal to do so.

Good tune up: 1: spark plugs, cap, wires, 91 octane at 3/4 tank full of gas.

***If your car idles good at 25* BTDC the: 1. bad/loose timing chain, 2. You must clean your IACV on the back of your intake manifold.****

Bad MAF, and even bad TEMP sensor will also contribute to smog issues. HOT block = bad smog.

IT IS SO GREAT TO FIND AN HONEST SMOG PERSON THAT LOVES S13'S AND JDM CARS!

[shin_viro]

dude this thread helps so much. thanks veracity84

[mxexux]

Instead of telling you whats wrong with your car (which could be several things). I will tell you what each of the gasses mean:

HC = Hydro Carbons = Unburnt fuel or Oil.
Possible causes: Cylinder misfires; Oil getting into the combustion chamber.

CO = Partially burned Fuel
Possible cause: A/F mixture too rich.

NOx = Oxides of Nitrogen = Combustion temps high; Nitrogen bonds with Oxygen.
Possible causes: EGR system.

CO2 (For CA) = Carbon Dioxide = Normal Byproduct of gasoline burning.
Good healthy running engine should have ~15% emitting (CAT could filter some out)

Hopefully now you will have a better idea of whats going on inside the combustion chambers of your engine; which should help you narrow down the things that may need repairing.