HC Emissions Failed !

Supraholic

New Member
Mar 31, 2005
125
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Houston, TX
My 87T (5spd) failed emissions today. It passed CO and NO levels (at about 50% of the spec value). The emissions are checked at 15 mph and 25 mph in Virginia. HC level was 108 ppm (limit is 108ppm) at 15 mph and 181 ppm (limit is 105ppm) at 25 mph.

Mods include: Lexus AFM with screw half way in, RC 550 injectors, AFPR, WB high flow fuel pump, Magnacore plug wires, Random tech 3" downpipe, hi-flow cat, and 3" cat back. Fuel pressure was set at 25 psi at the time of the test. I passed with this setup two years ago.

OEM plugs are 4 years old with 20K miles on. will changing the plugs help? any tricks to get this to pass ?? what about screwing the AFM screw all the way out ? will the car just rich the mixture more to compensate? should I fool around with the EGR at all?

Any help is appreciated..
 

Iron Tank

Grease Monkey
Mar 30, 2005
44
0
0
49
N. California
Supraholic said:
My 87T (5spd) failed emissions today. It passed CO and NO levels (at about 50% of the spec value). The emissions are checked at 15 mph and 25 mph in Virginia. HC level was 108 ppm (limit is 108ppm) at 15 mph and 181 ppm (limit is 105ppm) at 25 mph.


What were your O2, CO2, and CO readings exactly at 15 and 25?
 

Iron Tank

Grease Monkey
Mar 30, 2005
44
0
0
49
N. California
Supraholic said:
My 87T (5spd) failed emissions today. It passed CO and NO levels

should I fool around with the EGR at all?

The operation of the EGR system effects the Nox emission. Since you you say it passes for levels of Nox , You should look elsewhere.
 

mrnickleye

Love My Daily Driver !
Jun 8, 2005
825
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0
Mojave Desert, Ca
I am a service manager at a smog test and repair shop in calif. and I smog tested cars for years. I see these situations every day, because when they fail at the 'test only' shops, they come to us for diagnosing and repairs.

If it is running real nice for you, with no misfiring, then plugs and parts aren't gonna help much. If you lean it out too much (dropping the CO) you run a rick of raising the NOX, and causing a lean misfire, which will raise the HC higher. If the CO is around the average measuement or less, and the nox is too, then I would test the O2 sensor first (Bosch are around $35-$50). If its good, then a cat converter will drop the HC down enough to pass.

The #s you described will go way down with a new cat conv. but/and if the O2 is not working properly, a new one may fix your problem. If the O2 is original, go ahead and replace it yourself. Can only help with fuel mixture/economy.

We charge $149.95 installed for the cat you need. Magnaflow is mostly what we use, because they last for many many years. If you are planning on keeping the car for a few years, don't get the cheapy ones that are out there (one pass cats) cause you'll be replacing it next test time.
 

Supraholic

New Member
Mar 31, 2005
125
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0
Houston, TX
Thanks for all your replies.. Here is the CO and NOx numbers from the test:

15 MPH
CO: 0.13% (Limit 0.61%)
NO: 381 ppm (Limit 823ppm)

25 MPH
CO: 0.38% (Limit 0.64%)
NO: 570 ppm (Limit 750ppm)

The Random-Tech 3" High-Flow cat is about 2.5 years old. The exhaust pipe is very black .. must be carbon from running too rich.. may be the cat is also coated with carbon..that the catalyst is not doing the right thing... may be will a magnaflow cat fit this 3" exhaust setup?
 

JtWo

Sniper
Apr 10, 2005
159
0
0
Bay Area
I also failed my test here in california today. Passed everything except emissions.

15 mph
HC: 174(max 106)
NO: 3713(max 762)

25 mph
NO: 1856(701)
 

tte

Breaking In - in progress
Mar 30, 2005
940
0
0
Northern California
Go to a local race shop and buy ethanol. Thats what I did.

I put in 2 gals when I was almost out of fuel....went straight to the smog station and passed. I also moved the airflow meter half out too..thats it...

Cheers,
Roy
 

Supraholic

New Member
Mar 31, 2005
125
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0
Houston, TX
I like the ethanol idea.. will that cause any sensors to go bad? like the O2 sensor or some??? or what if I mix one gallon of gas and one gallon of ethanol ? but then again, when the fuel gauge shows empty, there is still good amount of gas in tank right??
 

Iron Tank

Grease Monkey
Mar 30, 2005
44
0
0
49
N. California
Supraholic said:
Thanks for all your replies.. Here is the CO and NOx numbers from the test:

15 MPH
CO: 0.13% (Limit 0.61%)
NO: 381 ppm (Limit 823ppm)

25 MPH
CO: 0.38% (Limit 0.64%)
NO: 570 ppm (Limit 750ppm)


C02 = ?
O2 = ?
To be able to acurately diagnose the problem we need all 5 gas readings.
Based on what you have given me, I'd check o2 sensor operation. I'd also suspect the catalyst. Do you still have the Light off cat in place?
 
Last edited:

Iron Tank

Grease Monkey
Mar 30, 2005
44
0
0
49
N. California
JtWo said:
I also failed my test here in california today. Passed everything except emissions.

15 mph
HC: 174(max 106)
NO: 3713(max 762)

25 mph
NO: 1856(701)


Looks like your combustion temps are getting very high. Could be due to a severe vacuum leak, malfunctioning egr system or possibly a dead o2 sensor. I would check those first.
 

Supraholic

New Member
Mar 31, 2005
125
0
0
Houston, TX
Iron Tank said:
C02 = ?
O2 = ?
To be able to acurately diagnose the problem we need all 5 gas readings.
Based on what you have given me, I'd check o2 sensor operation. I'd also suspect the catalyst. Do you still have the Light off cat in place?

The only other information in my inspection report is the dilution number:
at 15 MPH
Dilution is 14.1
at 25 MPH
Dilution is 13.9

As I understand, the dilution at the optimum condition is 14.7 Both cases here, i am below that.. (too rich).. Also, I checked the Vf reading yesterday at 2500 rpm (car in neutral). Vf voltage was 4.99 volts.
My random technology high flow cat is less than 3 years old. I dont know what the condition of the brick inside..
 

tte

Breaking In - in progress
Mar 30, 2005
940
0
0
Northern California
Ethanol will attack the rubber components of a fuel system if used for long periods of time.

You will only be using it for smog which will be at most 1/2 hour so you should be okay. After you pass the smog just fill your tank up with gasoline.
I got my ethanol from a race company for a 6 pack of beer.

A couple of race companies I know said so too and they know about ethanol as they race ethnanol/methanol fuel cars.

Cheers,
Roy