Failed OBD1 emissions - emission gurus

[jfman]

And if you dont know what your talking about, dont post, anybody can say "put a new cat and 02 sensor on it"


Car : bone stock 1993 300z

It failed the NOx ppm reading.... What can be the cause of that.


the reading was 2321 and the limit is 907

It passed the HC-ppm and CO% with flying colors.

I want to know what this means..

[BTEC]

PUT SOME CATS ON DAT SUM BITCH

[yudalicious]

possibly EGR system? high NOx = too high combustion temp, irrc EGR helps lower combustion temp...
also check timing.

[BTEC]

possibly EGR system? high NOx = too high combustion temp, irrc EGR helps lower combustion temp...
also check timing.
TRUE AS WELL. EGR VALVES USED TO GO BAD ON THE MAIL TRUCKS I USED TO WRK ON ALL TE TIME.

[BTEC]

And if you dont know what your talking about, dont post, anybody can say "put a new cat and 02 sensor on it"


Car : bone stock 1993 300z

It failed the NOx ppm reading.... What can be the cause of that.


the reading was 2321 and the limit is 907

It passed the HC-ppm and CO% with flying colors.

I want to know what this means..
I SEE U EDITIED UR POST. IM ASSUMING U THINK I WAS BSING U BY THE WAY I POSTED BUT THE TRUTH IS IM PROLLY RIGHT. UR CATS ARE A SOURCE OF BACK PRESSURE. IF THEY GO BAD AND THE ACTIVE MATERIAL IN THEM COM OUT IT WILL TO AN EXTENT CAUSE UR EXHAUST TO FLOW ALOT BETTER CAUSING UR CYLINDERS TO GO LEANER WHICH INCREASES UR CYLINDER TEMP. DO U HAVE NEW CATS ON THE CAR?

[jfman]

The HC's are at 32(120 allowed) and the CO's are .02(.67 allowed)


Why would it do so well on those and fail miserably the NOx ?


Wouldnt it do bad with those too if the cats were bad ?

[BTEC]

The HC's are at 32(120 allowed) and the CO's are .02(.67 allowed)


Why would it do so well on those and fail miserably the NOx ?


Wouldnt it do bad with those too if the cats were bad ?
HC'S ARE UNBURNED FUEL SO IF IT LEAN THEN THEY WOULD BE LOW(LIKE UR READINGS). I HAVENT WRKD IN A SHOP IN A WHILE SO IM A LIL RUSTY BUT I HAVENT FORGOTTEN ALL MY DRIVEABILITY SKILLS. I CAN TELL U HOW TO TEST UR CATS IF U HAVE ACCESS TO A LASER TEMP GUN OR SOME KINDA WAY TO TELL THE TEMP GOING IN AND OUT OF THE CATS.

[SLow_POke]

HC'S ARE UNBURNED FUEL SO IF IT LEAN THEN THEY WOULD BE LOW(LIKE UR READINGS). I HAVENT WRKD IN A SHOP IN A WHILE SO IM A LIL RUSTY BUT I HAVENT FORGOTTEN ALL MY DRIVEABILITY SKILLS. I CAN TELL U HOW TO TEST UR CATS IF U HAVE ACCESS TO A LASER TEMP GUN OR SOME KINDA WAY TO TELL THE TEMP GOING IN AND OUT OF THE CATS.

BTEC!!! Im a lil rusty myslef but you got it pretty well man.:goodjob:

also a clogged cat while give you HIGH Nx.
LIke BTEC said if you have a heat temp gun you while more then deff rule out/in the cat IF* its bad .

I also seen Dirty MAF give you high nox


-Ernie

*EDITED*
and i jsut saw you co's seems reslly low LEAN MISFIRE>? vac leak possible

[SLow_POke]

The HC's are at 32(120 allowed) and the CO's are .02(.67 allowed)


Why would it do so well on those and fail miserably the NOx ?


Wouldnt it do bad with those too if the cats were bad ?

Its a combination of ALL the 5 gases that deteermines a problem or leads you in the right direction.

-Ernie

[Lucient]

Your EGR valve isnt working properly. How old are the cats on the car? My KA wouldnt pass for the same reason last year and I had great CO and HC readings. Repair or replace the egr valve and when you get it re-tested do the low speed test in first gear and the high speed test in 2nd gear. This will get the engine rpms up and still be within the rpm parameters

[Smokin_Joes_2kSi]

if it's a honda, *COUGH* chip ecu, crome pro, lean it out...TADAH!!!
emissions done!
Joe

[SLow_POke]

if it's a honda, *COUGH* chip ecu, crome pro, lean it out...TADAH!!!
emissions done!
Joe



And if you dont know what your talking about, dont post, anybody can say "put a new cat and 02 sensor on it"


Car : bone stock 1993 300z

It failed the NOx ppm reading.... What can be the cause of that.


the reading was 2321 and the limit is 907

It passed the HC-ppm and CO% with flying colors.

I want to know what this means..


TADA!!!!!!!!!!!!!!!!!!

[JKNOUSE]

my 300zx n/a failed to but they told me the car has to be running for about 25 min or longer so i want back 30mins later and it past
so maybe you didnt give the car time to warm up.
thats all i got for u

[Z U L8R]

i wouldn't be at all surprised if you need cats, and your egr valve's sticking BUT! check those hoses on each side of the down pipe ( the bent part right after the exhaust manifold ) and see if those are there/intact. but Nitrous oxides is almost always a cat or egr problem, and someone mentioned up there timing, that can be true too, if the timing is too advanced your cylinder head temp will be high resulting in more nox but first see if those hoses are there and start shopping for cats......on vg30dett cats rob about 40hp so a lot of TT guys go straight pipe, ask one for their cats ^_^ friggin car's got 4 of them bitches

[Z U L8R]

those hoses connect the exhaust to the egr tubes which feed the exhaust gas through the egr valve. the exhaust gas recirculation valve puts that gas in the intake manifold and the engine reburns it which lowers cylinder head temp thus lowering nox. it's a different world from emissions to performance with a pretty thin barrier. performance car you would want cold/denser air ingested into the engine giving more power and engine running leaner, but with that comes higher nox. by recirculating the hot exhaust gas the air in the plenum is not as dense therefore the car's not going to run as lean thus lowering cylinder head temp and nox. also another reason you'll notice on nissan motors how it has coolant running through the throttle body. just wanted to help you understand the WHY in how does shooting hot gas into my engine cool it down. personally though i still think your nox is too high to be just egr related, i'd still recommend sourcing some cats.

[3kgtdrvr]

whats the co2 and 02 readings?

[LQQKITZME]

clogged injectors = high cyl temp too

[Z U L8R]

vg injectors usually don't clog they usually corrode and don't fire after you take the plugs off LOL, you gotta clean all the green shit outta em before they fire again.

if i had your car at my shop i'd check the egr valve/egr vac switch/exhaust temp sensor/etc to see if it's functioning and or if the egr passages are clogged, THEN i'd most likely condemn the cats LOL. if you don't know how to check the egr system msg me.

another thing that can cause nox to soar is if you don't have a thermostat. your car will never reach operating temperature but usually the nox'll be like 3000-4000ppm
:ninja:

[3kgtdrvr]

noX arent created until cylinder combustion chamber temps reach 2500 degrees fahrenheit. if you have no thermostat or its stuck open then the car would run cooler and richer and would create more HC's.

you are not running rich bc co is down and co is a rich indicator. this is why i asked for your o2 and co2 reading. it will tell you if you are running lean or at stoichiometric ratio. you can also run lean and up with low nox bc if its gets too lean then you will get a lean missfire and you will not have complete combustion. this obviously isnt the case bc ur hc is low. you can still run lean though...thats why we need to know the o2 and co2

everyone did have good ieads about the egr and cat and too adcaned ignition timing, but we need to see what the other readings are before we can decide what it is bc its all speculation and assuming only makes an ass out of u and me :goodjob:

[3kgtdrvr]

p.s. if you have high co, you will never have nox...theyre not positively related. if youre running rich, combustion temperatures stay lower and it wont get hot enough to create them

and 300zx's are bad for doing this so dont worry

[Z U L8R]

no thermostat will make the car run cooler and richer which will make the hc's go up but in THIS case his hc's are fine. I was talking about possible causes of nox which is why i mentioned it. What happens when the computer detects it's running rich? "this car's running rich, i better lean it out" and when it leans it out the nox go 3500+ppm, this isn't THIS 300zx's problem i was just giving more educational info that's why i said IF that were the case it'd be more like 3000-4000 which it's not. :P BUT ANYWAYS lol

hc's are 32(120 allowed) co's .02(.67 allowed) 2321 nox (907 allowed)

run car at idle put vacuum to egr valve, if car dies egr valve & ports are good, if egr valve doesn't open with vacuum then egr valve is bad, if egr valve opens and car doesn't attempt to die or die then the egr ports are restricted/clogged. if egr never gets vacuum at all then investigate why the vac switch isn't supplying vacuum, if you don't want to go through the tests and just want your car to pass, buy some cats :D