C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

failed emissions

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Old Feb 21, 2006 | 07:46 PM
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Default failed emissions

I guess this is the night for it. I read bownblu's thread with interest.
Mines worse than his but I think I know why.
My HC = 8.72 my CO is 162.9 Both fail by a mile.
I pass the NOx with a .70
What does any of that mean?
Also before you read the next paragraph .What do you think is causeing those failures?
Ok hears what I think.
After passing last time,2 years ago.
I put back in my 160 therm.& 190 fan switches.
I completely forgot I did that , thought I was gonna fast pass.
But Nooooooooo.
So whould running hotter fix HC & CO?
What affects HC & CO?
Its an 84 with high mileage,But brand new heads.
Thanks guys Your great.
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Old Feb 22, 2006 | 01:44 AM
  #2  
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Hydro carbons and Carbon Monixide..
Burned and unburned fuel.
Usually high Hydrocarbons are unburned fuel.
Try this stuff ,it might help.
http://www.bgprod.com/
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Old Feb 22, 2006 | 01:49 AM
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unburnt fuel? you are running way rich... which is a side effect of that low t-stat and fan setting. I would be surprised if the engine was in closed loop at the time it was tested.

loose them.

Read this thread: The Renamed T-stat

Running that rich will kill a cat, too.

And cats thrive on heat. Any chemical fix is only going to mask the real problem.
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Old Feb 22, 2006 | 01:52 AM
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Originally Posted by 7thvet
I guess this is the night for it. I read bownblu's thread with interest.
Mines worse than his but I think I know why.
My HC = 8.72 my CO is 162.9 Both fail by a mile.
I pass the NOx with a .70
What does any of that mean?
Also before you read the next paragraph .What do you think is causeing those failures?
Ok hears what I think.
After passing last time,2 years ago.
I put back in my 160 therm.& 190 fan switches.
I completely forgot I did that , thought I was gonna fast pass.
But Nooooooooo.
So whould running hotter fix HC & CO?
What affects HC & CO?
Its an 84 with high mileage,But brand new heads.
Thanks guys Your great.
From a fundamental combustion standpoint, it is a balance between combustion temperature (higher temperature forms more NOx-required for the reaction) and the excess HC/CO (unburned fuel). Depending on the condition of the engine/tune it should pass without too many issues. It sounds like it is running rich or the catalytics are not working.. The cooler engine will run richer.

But in addition there are many other possibilities associated with this failure besides the fan/Tstat temp, so I would recommend hitting up the basics including spark plugs, O2 sensors, checking codes, etc....

Richard
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Old Feb 22, 2006 | 06:32 AM
  #5  
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You guys have no idea how much this post has me feeling as I failed emissions as well. I put about 100 miles on the car in a year. When I had the emissions checked last year it passed easily. The only thing that has changed is that I had replaced the battery about a month earlier. Only about 50 miles on the new battery. I replaced the plugs and learned just how hard they are to change but really it was kind of fun getting to learn more about this car. Anyway, since it hadn't been ran in quite a while I let it warm up and then kind of made some hard runs. Well, there was alot of smoke pouring out at first but then that went away. Now let me say that when I changed the plugs I noticed the passenger side plugs were really bad as compared to the drivers side. Also let me say that this car is bonestock. I am going to try the above items for possible fixes to this problem.
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Old Feb 22, 2006 | 08:47 AM
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Thanks guys.
I'll try making it run hot & retest.I'll let ya know my results.
Thanks again.
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Old Feb 22, 2006 | 09:21 AM
  #7  
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Originally Posted by bogus
unburnt fuel? you are running way rich... which is a side effect of that low t-stat and fan setting. I would be surprised if the engine was in closed loop at the time it was tested.

loose them.

Read this thread: The Renamed T-stat

Running that rich will kill a cat, too.

And cats thrive on heat. Any chemical fix is only going to mask the real problem.
Reply
Old Feb 22, 2006 | 07:15 PM
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Thanks guys.
You have made me feel that the temp sender isnt going to fix it.
I spoke to 2 different Mechs. today they both think the same as you.
I checked & I do have the 195 therm. installed.
I bought the correct fan switch & installed it.
So I drove around for a while got the fan to cycle. If I idle a while the engine will get hot.But If I drive it runs at 185 degrees so thats not going to help.
So anyway the second mech. said for $100 they will tell me whats wrong, Ive been dicking with this thing sence I bought it in 99, so a hundred bucks,WTH. Im gonna spend the money.
I have an appointment on monday.
Thanks for your help. I'll be back with more info.
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Old Feb 22, 2006 | 07:54 PM
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Seven years trying to pass a smog rest? THAT may be a record.

RACE ON!!!
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Old Feb 22, 2006 | 08:01 PM
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Originally Posted by CFI-EFI
Seven years trying to pass a smog rest? THAT may be a record.

RACE ON!!!
No it passed 2 years ago & prior years, its just always loaded up when cold, I dont know why its not passing now because nothings different ( now that I put the right fan switch in) than 2 years ago.
It runs great I beat a 97 Z/28 6 speed.
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