Failed Emissions
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Failed Emissions
.............................. HC.................CO................... NOx
State Standard........1.8000 gpm.......30.0000 gpm........2.8000 gpm
Inspection Reading....2.6924 gpm........6.2691 gpm........1.1040 gpm
Inspection Results......FAILED.............PASS.... ...............PASS
The test is done on a dyno. The car is driven at various speeds up to 60mph. The readings are averaged but a diagnostic trace is also available. Mine shows HCs staying above the state threshold most of the time. It only dips below the threshold at speeds over 50 mph. The trace spikes upwards at idle. The test tech suggested that it's running rich.
Here's work that's been done on the car in the last 3k miles:
Plugs, wires, distributor cap and rotor, PCV valve, air filter, fuel filter, O2 sensor, set timing 8 degrees. The car runs strong and throws no codes.
I did a search on emissions and came up with a few threads. The consensus seems to be that I should retard the timing to 6 or even 4 degrees. What else should I look at?
[Modified by Eric Fraser, 10:25 PM 2/13/2002]
State Standard........1.8000 gpm.......30.0000 gpm........2.8000 gpm
Inspection Reading....2.6924 gpm........6.2691 gpm........1.1040 gpm
Inspection Results......FAILED.............PASS.... ...............PASS
The test is done on a dyno. The car is driven at various speeds up to 60mph. The readings are averaged but a diagnostic trace is also available. Mine shows HCs staying above the state threshold most of the time. It only dips below the threshold at speeds over 50 mph. The trace spikes upwards at idle. The test tech suggested that it's running rich.
Here's work that's been done on the car in the last 3k miles:
Plugs, wires, distributor cap and rotor, PCV valve, air filter, fuel filter, O2 sensor, set timing 8 degrees. The car runs strong and throws no codes.
I did a search on emissions and came up with a few threads. The consensus seems to be that I should retard the timing to 6 or even 4 degrees. What else should I look at?
[Modified by Eric Fraser, 10:25 PM 2/13/2002]
Team Owner
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From: Dallas TX
Re: Failed Emissions (Eric Fraser)
Retard it and it will drop the HC's ... but your NOx's will go up. Looks like you have plenty of room to go up in the NOx area, so that should help.
I'm going to have the same problem as you. With a bigger cam more unburned fuel is going to flow out the back (Hydro Carbons), so I'm going to have to try and lean it out enough that it will pass ... all this while not making my NOx's go through the roof. I might also just go to a "special" station... :blueangel:
[Modified by Glock'94, 12:38 AM 2/14/2002]
I'm going to have the same problem as you. With a bigger cam more unburned fuel is going to flow out the back (Hydro Carbons), so I'm going to have to try and lean it out enough that it will pass ... all this while not making my NOx's go through the roof. I might also just go to a "special" station... :blueangel:
[Modified by Glock'94, 12:38 AM 2/14/2002]
Le Mans Master
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From: Manassas VA
Re: Failed Emissions (Eric Fraser)
Eric,
This is just a guess, but if it was my car I would put the 195 t-stat back in and set the fans back to the orig. setting. I was told by a friend that did emissions inspections to have the car as hot as possible and run it hard before bringing it in. Good luck.
This is just a guess, but if it was my car I would put the 195 t-stat back in and set the fans back to the orig. setting. I was told by a friend that did emissions inspections to have the car as hot as possible and run it hard before bringing it in. Good luck.
Team Owner
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From: SE NY
Cruise-In II Veteran
Re: Failed Emissions (Eric Fraser)
You might get a hi-flow Catco cat from Summit for under $100. I suspect the stock cat may be about done for.
Since you have new ignition and O2 sensor and a 180 deg stat I would look to the cat.
I ran a 180 deg stat and 160 deg fan sw on my '86 IROC and recently passed Ohio's dyno E-check after I installed a new O2 sensor.
Indeed have the engine warm before the test and run it at a fast idle (about 1k rpm) while waiting as the cat and O2 sensor tends to cool at slow idle.
You might try a scan tool to assure that it stays in closed loop at idle.
Since you have new ignition and O2 sensor and a 180 deg stat I would look to the cat.
I ran a 180 deg stat and 160 deg fan sw on my '86 IROC and recently passed Ohio's dyno E-check after I installed a new O2 sensor.
Indeed have the engine warm before the test and run it at a fast idle (about 1k rpm) while waiting as the cat and O2 sensor tends to cool at slow idle.
You might try a scan tool to assure that it stays in closed loop at idle.
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Re: Failed Emissions (Red 86 4+3)
Thanks Red,
I thought of that and might still do. Sort of return the car to factory specs for the test. At the test I had fully warmed up the car and the oil as well as the coolant were both at about 200 degrees. Would a hot engine (say 230 degrees as opposed to 200 degrees) run leaner?
I thought of that and might still do. Sort of return the car to factory specs for the test. At the test I had fully warmed up the car and the oil as well as the coolant were both at about 200 degrees. Would a hot engine (say 230 degrees as opposed to 200 degrees) run leaner?
Eric,
This is just a guess, but if it was my car I would put the 195 t-stat back in and set the fans back to the orig. setting. I was told by a friend that did emissions inspections to have the car as hot as possible and run it hard before bringing it in. Good luck.
This is just a guess, but if it was my car I would put the 195 t-stat back in and set the fans back to the orig. setting. I was told by a friend that did emissions inspections to have the car as hot as possible and run it hard before bringing it in. Good luck.
Team Owner
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From: Boston, Dallas, Detroit, SoCal, back to Boston MA
Re: Failed Emissions (Eric Fraser)
You could also try a little alcohol
Now that I'm back in (cough) Taxachuesetts, I found out that I need to due a roller test as well.
Some members here ;) get out of the roller test because thier car has traction control, and "cannot" be turned off :yesnod:
Now that I'm back in (cough) Taxachuesetts, I found out that I need to due a roller test as well.
Some members here ;) get out of the roller test because thier car has traction control, and "cannot" be turned off :yesnod:
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Re: Failed Emissions (David-F)
I'm the original owner and I have not removed or gutted the cat. I'm on my second one. Replaced it at 120k. Does the fact that the NOx and CO readings are low mean that the cat is probably working?
Do you still have a cat on the car it looks like it's been removed or gutted.
David Fulcher
David Fulcher
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From: Boston, Dallas, Detroit, SoCal, back to Boston MA
Re: Failed Emissions (Eric Fraser)
try some dry gas first
but your cars not that modded.
There are guys out there with hotcams passing calf emmisions.
at 120k you might want to due a leak down test.
also check for vacuum leaks
no code? wierd...
[Modified by BrianCunningham, 2:16 AM 2/15/2002]
but your cars not that modded.
There are guys out there with hotcams passing calf emmisions.
at 120k you might want to due a leak down test.
also check for vacuum leaks
no code? wierd...
[Modified by BrianCunningham, 2:16 AM 2/15/2002]
Le Mans Master
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From: Santa Maria, CA
Re: Failed Emissions (Eric Fraser)
read this: http://forums.corvetteforum.com/zerothread?id=230322
I understood that the cats don't like alcohol, so I dumped in a bottle of octane booster.
I understood that the cats don't like alcohol, so I dumped in a bottle of octane booster.
Drifting
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From: Woodstock GA
Re: Failed Emissions (Eric Fraser)
No the cat is more for Hc, NOX is EGR operation it's because it's so close and the CO is low or should I say were it should be that seems to point to a week or missing cat. But I do have one more question did you replace the O2 sensor with the correct A/C Delco sensor if not that could be the problem I have seen that many times also many aftermarket sensors are not of the same calibration as the factory ones are so everything will work fine just shifterd enough to fail an emission test.
David Fulcher
P.S. I am a firm believer in that if a car is running the way it should be with the correct O2 sensor and a good working cat it should be able to pass an IM240 test with maybe the exception od NOX if the car has had the EGR removed or is not working, you shouldn't have to add stuff to the gas to get it through
David Fulcher
P.S. I am a firm believer in that if a car is running the way it should be with the correct O2 sensor and a good working cat it should be able to pass an IM240 test with maybe the exception od NOX if the car has had the EGR removed or is not working, you shouldn't have to add stuff to the gas to get it through
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Re: Failed Emissions (David-F)
Thanks David,
I used a Bosch O2 sensor from Advanced Auto Parts. Maybe I should look for an A/C Delco unit, huh?
I used a Bosch O2 sensor from Advanced Auto Parts. Maybe I should look for an A/C Delco unit, huh?
But I do have one more question did you replace the O2 sensor with the correct A/C Delco sensor.
Thread Starter
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Re: Failed Emissions (BrianCunningham)
Actually 120k is when I replaced the cat. I'm closer to 168k at this point. Leaking injectors did cross my mind. Would leaky injectors leave any tell tale signs on the old spark plugs? They looked pretty normally worn when I changed them.
At 120k you might want to due a leak down test.
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From: The Top of Utah
Re: Failed Emissions (Eric Fraser)
I don't know if this is relevent to your situation or not. The ONE time I had a problem with a smog test, the problem was with the EGR valve. I had never heard of this before, but the return spring for the valve had grown weak with age. The valve was opening too far and causing a "lean misfire". The misfire caused the tailpipe emissions to be high in HC (rich). Since the EGR controls NOX and your NOX is low, I thought, possibly...
A rich mixture won't really cause abnormal plug wear, but a grossly rich mixture will leave a black fluffy residue on the plugs. A slight injector leak could be the problem. Does the fuel system maintain pressure after sitting a while?
A fresh oil change is also a good idea. Any gasoline that may have made it's way to the crankcase can enrichen the mixture, via the pcv system.
Good luck. It's a pain in the butt, but you'll get it.
A rich mixture won't really cause abnormal plug wear, but a grossly rich mixture will leave a black fluffy residue on the plugs. A slight injector leak could be the problem. Does the fuel system maintain pressure after sitting a while?
A fresh oil change is also a good idea. Any gasoline that may have made it's way to the crankcase can enrichen the mixture, via the pcv system.
Good luck. It's a pain in the butt, but you'll get it.
Drifting
Joined: Mar 2000
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From: Woodstock GA
Re: Failed Emissions (Eric Fraser)
Leaking injectors would give you a hard start especialy hot but it would have to be real bad for the ECM not to be able to compensate for this. My gut feeling is it could be the aftermarket O2 sensor, but then again if you used an aftermarket cats they may not last as long at factory(which shoule be the life of the car, most of the time cats get murdered)
David Fulcher
David Fulcher
Drifting
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From: Woodstock GA
Re: Failed Emissions (Nathan Plemons)
I didn't murder mine, I let them run free.
[/QUOTE]
That wasn't quite what I ment! What I ment was tthat most of the time a cat is damanged by bad wires or plugs or excessive rich fuel ratio for some reason.
David Fulcher
Drifting
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Re: Failed Emissions (Eric Fraser)
Your lucky on haveing higher standards .Heres what they are in Missouri.
MO STANDARD = HC 0.8 CO 15.000 NOx 2.0
My readings are = HC 3.4 CO 18.33 NOx 2.67
My 84 Failed thursday.
I appreciate all the input on this thread,it gives me some ideas what to do.
I think I'll repace my gutted cat,Change my IACs as there probably the originals,Change fan switch back to factory,And repalace the EGR.
Also just a note ,You can also kill a cat by not haveing the air pump switching valves opperating correctly.
On the 84 air can be pumped to the air cleaner or the exhaust manifold or to the cat via that tube.It goes thru the tube during warm up to reduce emmissions quicker by warming the cat. So if your pumping air to the cat via the tube all the time it burns up the cat.
MO STANDARD = HC 0.8 CO 15.000 NOx 2.0
My readings are = HC 3.4 CO 18.33 NOx 2.67
My 84 Failed thursday.
I appreciate all the input on this thread,it gives me some ideas what to do.
I think I'll repace my gutted cat,Change my IACs as there probably the originals,Change fan switch back to factory,And repalace the EGR.
Also just a note ,You can also kill a cat by not haveing the air pump switching valves opperating correctly.
On the 84 air can be pumped to the air cleaner or the exhaust manifold or to the cat via that tube.It goes thru the tube during warm up to reduce emmissions quicker by warming the cat. So if your pumping air to the cat via the tube all the time it burns up the cat.