Emission Testing
Thread Starter
Intermediate
Joined: Nov 2003
Posts: 40
Likes: 0
From: McHenry IL
Emission Testing
I need some advice - I took my 94 in for emission testing and did not pass the HC test. Off by about .1. Took car to deliever and they checked everything out and found not codes for any problems and could not find any reason for not passing test. Took car back for retest and it still failed. Deliever said that it had to be the Catalyic Converters and that eventhough they did not test bad, that I should change them. Cost $2200. I did not do it, but read in the 101 projects for my corvette that the changing of the Cat. Conv was not a big deal and that it is done by dropping the exhaust system. Questions, have any of you had emmision problems, is it related to Cat. Conv? How offen do they go bad (I have 70,000 miles on car)? What if I change the O2 sensors (even though dealer did not seem to think that would help). Also where can I buy Cat. Conv. if I need them and do this myself? Sorry for all the questions - I don't want to spend $2200.
Snoozer
Snoozer
Melting Slicks
Joined: Jun 2004
Posts: 3,032
Likes: 4
2200 for replacing the Cat?! 
I know you have an lt1/4 and the setup is different then my l98... For starters you have two cats i believe...
anyway, on my l98, it took about half an hour to get my cat off, and another half hour to put it back on. I did not have to drop the exhaust at all...
I should really let the lt1/4 owners speak up though, how hard is it guys?
I know you have an lt1/4 and the setup is different then my l98... For starters you have two cats i believe...
anyway, on my l98, it took about half an hour to get my cat off, and another half hour to put it back on. I did not have to drop the exhaust at all...
I should really let the lt1/4 owners speak up though, how hard is it guys?
Elite Torch Red Member
Joined: Sep 1999
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Likes: 23
From: Exit 89 GSP,Lakewood,NJ The Land Of Mojo
Cental/South NJ Events Coordinator
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Changing the cats isn't hard.......once you get past the rusted bolts and hopefully not breaking any of them.
I've seen used ones going from $50-$300 for a pair.
Random Tech makes direct replacements but I haven't been able to find them on the net, saw it in a magazine, and I don't know the cost.
I've seen used ones going from $50-$300 for a pair.
Random Tech makes direct replacements but I haven't been able to find them on the net, saw it in a magazine, and I don't know the cost.
Safety Car
Joined: Apr 2003
Posts: 3,793
Likes: 9
From: VA
Get a second opinion first.
If the cats really are dead at 10yrs and 70k then you have other problems that killed them. In that case, you don't want to put new cats on until you are sure the rest is working right.
If the cats really are dead at 10yrs and 70k then you have other problems that killed them. In that case, you don't want to put new cats on until you are sure the rest is working right.
Race Director
Joined: Aug 2002
Posts: 16,024
Likes: 0
From: Stratford Ontario
From what I understand (I failed also) an indicator of bad cat (s) is a high NO level, not HC. I had very high NO levels and I KNOW I have at least one bad cat. I'd get a second opinion as mentioned.
Race Director
Joined: Aug 2002
Posts: 16,024
Likes: 0
From: Stratford Ontario
Originally Posted by DieL
i just pay $150 and they stick a beater on the machine. just call in the vin and pick up the papers half an hour later 
around our parts it gives us 12 months of relief.......in the pocket book. BTW who do you know?, my guy won't help me like that. 
I guess either way I'll have to fix the sheit eventually.
Racer
Joined: Aug 2004
Posts: 379
Likes: 170
From: Buffalo Grove IL
Originally Posted by -=Iron Mike=-
From what I understand (I failed also) an indicator of bad cat (s) is a high NO level, not HC. I had very high NO levels and I KNOW I have at least one bad cat. I'd get a second opinion as mentioned.
So, it's possible the reduction section is working ok, but the oxidation section isn't. I don't have an LT1, but I'd venture to guess that possibly your AIR pump isn't working correctly (also there should be a line from the AIR pump to the converter, maybe that's not sending air correctly?) or maybe it's just running too rich (or misfiring) and the converter can't process the excess HC?
How do your plugs look?
Ben
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Thread Starter
Intermediate
Joined: Nov 2003
Posts: 40
Likes: 0
From: McHenry IL
emissions
Originally Posted by bmalec
You're correct, HC is unburnt fuel.
Ben
Ben
I will check later for other replies.
Snoozer
Le Mans Master
Joined: Dec 2002
Posts: 6,715
Likes: 2
From: Santa Teresa New Mexico
Originally Posted by Snoozer
Thanks for all the replies. I will have to get another opinion. What baffels me, is that the dealer could not find anything wrong with how the engine is running. I would have thought that is the air pump or others things were not working, they would have found it.
I will check later for other replies.
Snoozer
I will check later for other replies.
Snoozer
When the machine is hooked to the car (ie piped) the machine is in contact with the local dept of motor vehicles. If you don't pass the DMV flags the test. They keep a record.
To do a pre-test the machine checks the car emissions without the dmv knowing about it. That way if you fail its not recorded.
HC hydrocarbons is as stated earlier un-burned gasoline.
A good tune good go along ways here. Also have the car tested with a diagnostic computer to check for a failed cat or 02 sensor.
It is possible that a bad or malfunctiong MAS could be at fault.
Theres a myriad of problems that could cause a bad reading.
PLugs, injectors, mas, cat, I've seen them all cause a bad test.
A diagnostic computer is the fastest way to finding the problem.
Some tune-up shops guarentee a pass.
Good luck.
Melting Slicks
Joined: Jul 2004
Posts: 2,695
Likes: 0
From: Chicago Illinois
The temperature of your cars engine could be the problem with passing the hc test. If you have 160 stat the engine is not hot enough to burn off all the hc's. Put the stock stat back in for the test and youll pass. This happened to me
