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Old 06-30-2007, 05:08 PM   #1
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Default Can't Pass Smog at 15MPH --> HCs and NOx too high

vtec with aem cai, greddy header and greddy exhaust with carsound/magnaflow cat (2.5").
carsound cat is 3k miles old (my suspicion is the cat, may need to get an OEM cat).

CAR RUNS EXTREMELY WELL WITH NO PROBLEMS!!!!

JUST DID THE FOLLOWING B4 GOING TO GET TESTED:
a) changed oil (Mobil 1)
b) changed O2 sensor (denso)
c) changed spark plugs (NGK)
d) cleaned out EGR ports and EGR itself of the carbon build up
e) timing is at 15 BTDC
f) ran G2P
g) dizzy is less than 5k miles old (king distributors)
h) coolant has been flushed last year
i) valves adjusted 4k miles ago
h) drove for 45 minutes

here are my numbers (please note how i not only fail all three at 15mph but how HC and NOx drop by a lot at 25mph to well below passing levels):

15mph
CO2 --> 14.01
O2 --> 0.44
hc --> 157 meas, max is 88 --> FAIL
co --> .58 meas, max is .52 --> FAIL
nox --> 1946 meas, max is 704 --> FAIL

25mph
CO2 --> 14.60
O2 --> 0.05
hc --> 53 meas, max is 53 --> PASS
co --> .05 meas, max is .50 --> PASS
nox --> 142 meas, max is 738 --> PASS

as you can see, my numbers pass at 25mph but fail at 15mph.

my guess for the culprit is the carsound catalytic converter which is less than 3k miles old... but i hear mixed reviews on these passing smog.

is my best going with a oem cat?

TIA!

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Old 07-01-2007, 03:39 PM   #2
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Default Re: Can't Pass Smog at 15MPH --> HCs and NOx too high (shl76)

i fail with g2p product, go get your money back from crc g2p company, it took a month to get my money back but it was worth it. timing is for 14btdc
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Old 07-01-2007, 03:45 PM   #3
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Default Re: Can't Pass Smog at 15MPH --> HCs and NOx too high (shl76)

you should have repair your car , not the state ref. state pays up $500 for smog repair, you should do it, it's worth it because your going spend money test after test after test. at smog repair shop they do diagnotic on your car to see what is wrong with.
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Old 07-02-2007, 07:56 AM   #4
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Default Re: Can't Pass Smog at 15MPH --> HCs and NOx too high (nokturnal_munkeeboy)

Well looking at the differences in the 02 readings, I would say the cat was not warmed up before the test. Or not efficient enough for the test.How long was the car sitting before the test?

Tell the tech that warming up the cat a bit is legal, What is illegal is super heating it.

.4 is more than I would like to see.

Did you do the test with the G2 stuff in the tank? Usually cleaners will raise the CO readings. Which in turn raise the HC's.
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Old 07-02-2007, 01:25 PM   #5
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Default Re: Can't Pass Smog at 15MPH --> HCs and NOx too high (shl76)

i failed too because my Nox was too high..... something above the 1000's....
what is the cause of high Nox reading???
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Old 07-02-2007, 02:32 PM   #6
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Default Re: Can't Pass Smog at 15MPH --> HCs and NOx too high (shl76)

You have very high CO2 readings which is good as its an indication of efficient combustion and should be free of serious mixture or misfire problems. 14-15% of CO2 is achieved at around stoichiometric mixture so you can isolate lean or rich problems. i highly suspect a bad/inefficient catalyst based on your readings, the asm dyno test are 50/15 and 25/25. At 15mph a load of 50% is applied instead of only 25% at 25mph so it is absolutely normal to fail at 15mph (more load) and pass at 25mph with a bad catalyst.
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Old 07-02-2007, 02:48 PM   #7
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Default Re: Can't Pass Smog at 15MPH --> HCs and NOx too high (b20vtech)

Quote:
Originally Posted by b20vtech
i failed too because my Nox was too high..... something above the 1000's....
what is the cause of high Nox reading???
NOx is increased when combustion temps exceed 2500 F and/or high combustion pressure, there are many things that can cause high readings. Lean air/fuel mixture, over advanced ignition timing, vacuum leak, decreased or no EGR flow, lower octane fuel, low fuel pressure etc etc ......
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Old 07-02-2007, 04:27 PM   #8
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Default Re: Can't Pass Smog at 15MPH --> HCs and NOx too high (thesmogman)

no i didnt go test while g2p product in my tank, it was days after i used the product.
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Old 07-03-2007, 02:12 PM   #9
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Default Re: Can't Pass Smog at 15MPH --> HCs and NOx too high (nokturnal_munkeeboy)

i put my money on egr valve.
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Old 07-03-2007, 06:03 PM   #10
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Default Re: Can't Pass Smog at 15MPH --> HCs and NOx too high (postman)

Quote:
Originally Posted by postman
i put my money on egr valve.
why do you say that?
with those hc and co readings, it is extremely unlikely.
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Old 07-04-2007, 10:20 AM   #11
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Default Re: Can't Pass Smog at 15MPH --> HCs and NOx too high (Flexmyrex)

Quote:
Originally Posted by Flexmyrex
why do you say that?
with those hc and co readings, it is extremely unlikely.
Yeah, but the EGR valve doesn't help HC or CO, it will help lower NOx.
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Old 07-04-2007, 10:28 AM   #12
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Default Re: Can't Pass Smog at 15MPH --> HCs and NOx too high (shl76)

Is this an OBDII car? If it is you can access what is called mode 6 and get readings from the PCM that tells you what the PCM saw when it tested the cat. They are usually min/max numbers with no units. For example, the minimum may be 0 and the maximum may be, say, 750. If it is anywhere between 0 and 750 the cat passes the test, if it is over 750 then it fails and the check engine light may come on. If the reading was, say, 125 this means the cat passes and is relatively efficient. If the reading is, say, 715 then it is close to the limit and is not very efficient and may be the cause of your problem. Most techs don't know about this though however it's been part of OBDII since 1996.
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Old 07-04-2007, 11:51 AM   #13
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Default Re: Can't Pass Smog at 15MPH --> HCs and NOx too high (Scott_Tucker)

how do you access mode 6.
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Old 07-05-2007, 08:12 AM   #14
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Default Re: Can't Pass Smog at 15MPH --> HCs and NOx too high (Scott_Tucker)

Quote:
Originally Posted by Scott_Tucker
Yeah, but the EGR valve doesn't help HC or CO, it will help lower NOx.
Scott I understand what your saying but the EGR valve does affect HC and CO indirectly. Usually with a faulty EGR you would see CO and HC drop because of the high combustion temps. Of course this is considering we have a mechanically sound engine with no fuel/ignition system problems.


Modified by Flexmyrex at 9:25 AM 7/5/2007
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Old 07-05-2007, 08:52 AM   #15
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Default Re: Can't Pass Smog at 15MPH --> HCs and NOx too high (Flexmyrex)

On the 90's honda's a stuck open EGR/solenoid will affect HC and CO. Poor combustion is the result from the additional exhaust gas not getting compensated for. Lean mis-fires. Usually NOX is very low with the additional HC's

On a OBDII car the EGR is more regulated with a pressure sensor sensing the flow of the EGR along with the position sensor and circut verification(Voltage)

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Old 07-06-2007, 07:23 AM   #16
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Default Re: Can't Pass Smog at 15MPH --> HCs and NOx too high (thesmogman)

it's an obd i car.

so from what i can see, looks like i should get a new oem egr and cat converter?
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