Now, Emissions, was: Conundrum: Pressurized air in fuel rail. How?
12-16-2006, 06:56 PM
#32
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Originally Posted by ZEUS+
How is it now ?
There were no available slots yesterday for testing. The owner's going to retest next week.
I'll post additional data as it comes in.
I also told the owner to manipulate the outlet fuel hose to see if he could coax a fuel drip from it. However, I'm betting that he's betting on the re-connected fuel vapor system and the less-old MAF to get him through.
12-18-2006, 10:12 AM
#34
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I hope he passes too, sorry I haven't been around guys, its a little crazy at work right now, I'm trying to get a number of things finished so I can leave for a week at christmas, hopefully... (sigh) I'd be interested to find out what the problem/problems actually turn out to be.
Bill said " I don't see what this has to do with failed NOx "
Well, in my mind, the way Worf described it thats alot of air. We're not talking at a particular injector malfunction..because its in the fuel rail itself and is under pressure that means its going to reduce the amount of fuel being introduced into the engine during any injector cycle across ALL EIGHT injectors at once. Thats gonna cause a lean condition that the LH is going to have to try and compensate for and I myself just can't see it being able to do that completely, which expains the high NOx. It would also explain why the car continues to run reasonably well and isn't trying to overheat, at least within the conditions that the car's being driven. Highway conditions are pretty easy on these cars, it might be different in a traffic jam. Lets just say that for the moment his cooling system is fairly robust and can handle the increased temps.
It is what it is. A crappy, clogged injector can cause high NOx but usually excessive HC are present as well. Because the hydrocarbons are low and the NOx is high that really suggests a lean condition to me for whatever reason and thats where I'd focus the diagnosis. Worf mentioned that many of the usual suspects such as O2, cats, MAF have been recently replaced. Well, I guess it doesn't hurt to double-check and make sure the said systems are working correctly, especially the O2.
Lets assume for the moment all of these items are working then where does it leave us? Don't forget about excessive carbon deposits, unlikely here but can cause high NOx, although that tends to have high HC's as well, same with a leaky cylinder again both would generally be present. The LH brain itself could be faulty, but as you guys were saying, the car runs relatively well with no other symptoms. Last but not least the pressurized air in the fuel rail. I still think thats a major contributor if not the main problem. Good luck with it guys.
Merry Christmas
Mark
Bill said " I don't see what this has to do with failed NOx "
Well, in my mind, the way Worf described it thats alot of air. We're not talking at a particular injector malfunction..because its in the fuel rail itself and is under pressure that means its going to reduce the amount of fuel being introduced into the engine during any injector cycle across ALL EIGHT injectors at once. Thats gonna cause a lean condition that the LH is going to have to try and compensate for and I myself just can't see it being able to do that completely, which expains the high NOx. It would also explain why the car continues to run reasonably well and isn't trying to overheat, at least within the conditions that the car's being driven. Highway conditions are pretty easy on these cars, it might be different in a traffic jam. Lets just say that for the moment his cooling system is fairly robust and can handle the increased temps.
It is what it is. A crappy, clogged injector can cause high NOx but usually excessive HC are present as well. Because the hydrocarbons are low and the NOx is high that really suggests a lean condition to me for whatever reason and thats where I'd focus the diagnosis. Worf mentioned that many of the usual suspects such as O2, cats, MAF have been recently replaced. Well, I guess it doesn't hurt to double-check and make sure the said systems are working correctly, especially the O2.
Lets assume for the moment all of these items are working then where does it leave us? Don't forget about excessive carbon deposits, unlikely here but can cause high NOx, although that tends to have high HC's as well, same with a leaky cylinder again both would generally be present. The LH brain itself could be faulty, but as you guys were saying, the car runs relatively well with no other symptoms. Last but not least the pressurized air in the fuel rail. I still think thats a major contributor if not the main problem. Good luck with it guys.
Merry Christmas
Mark
12-18-2006, 11:51 AM
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Bulletin: NOx went to 2100+ (700 limit) with less-old MAS and fuel vapor system connected. 
HC and C0 numbers are the essentially the same: 16 ppm and 0.01%
I'm going to send the owner instructions on how to read the O2 sensor.
HC and C0 numbers are the essentially the same: 16 ppm and 0.01%I'm going to send the owner instructions on how to read the O2 sensor.
12-18-2006, 02:59 PM
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Originally Posted by ZEUS+
Can you post all gas test results ?
Code:
HC CO % Nox Date 100 Lmt 0.32 Lmt 700 Limit Comment 3/5/2005 13 0.02 514 Last Passing Numbers 11/4/2006 13 0.01 1301 First fail 11/13/2006 ?? ?? 1200 After O2 Sensor R&R 12/11/2006 15 0.01 1971 After New Cats (928 SP X-over w/High Flow Cats) 12/18/2006 16 0.01 2139 After MAF Change and Fuel Vaper System Connection
12-18-2006, 10:34 PM
#38
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This is puzzling. It would be useful to have O2 results. To properly reduce NOx, the exhaust must be low in Os and the converter must have some CO to work with. Most converters can handle only about 2000 ppm NOx. This is why most manufacturers use an egr.
While it's difficult to have a NOx failure with a lot of CO present, high CO also causes carbon buildup in the combustion chamber and in the reduction portion of the converter. Even if you fix the CO problem, this carbon buildup remains. With CO low and the carbon buildup still there, you have the perfect conditions for NOx formation. Keep us posted on what finally resolves this problem.
While it's difficult to have a NOx failure with a lot of CO present, high CO also causes carbon buildup in the combustion chamber and in the reduction portion of the converter. Even if you fix the CO problem, this carbon buildup remains. With CO low and the carbon buildup still there, you have the perfect conditions for NOx formation. Keep us posted on what finally resolves this problem.
12-18-2006, 10:49 PM
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Originally Posted by ZEUS+
This is puzzling.
It would be useful to have O2 results.
To properly reduce NOx, the exhaust must be low in Os and the converter must have some CO to work with. Most converters can handle only about 2000 ppm NOx.
With CO low and the carbon buildup still there, you have the perfect conditions for NOx formation. Keep us posted on what finally resolves this problem.
If CO was high and/or HC was high we'd have some clues to work with.
12-19-2006, 02:21 AM
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Argh. MAF, O2 and cats and no better. What else can cause a very lean condition? You seem to have good fuel pressure. It's not clear whether the air/vapor in the rail was a red herring. I think someone already asked if you found the same thing on a cool engine, which would make that more interesting.
A gross intake air leak would be another possibility but it should cause idle issues. Still, looking for things like the breather line falling off the right side of the MAF boot, or a hole in that line, would be worth checking. I apologize if I missed that you already checked the breather and vacuum lines. For at least academic purposes it would be good to get a VOM on the O2 sensor.
A gross intake air leak would be another possibility but it should cause idle issues. Still, looking for things like the breather line falling off the right side of the MAF boot, or a hole in that line, would be worth checking. I apologize if I missed that you already checked the breather and vacuum lines. For at least academic purposes it would be good to get a VOM on the O2 sensor.
Last edited by Bill Ball; 12-19-2006 at 05:07 PM.
12-19-2006, 10:11 AM
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Guys, are you using the same test facility each time? Could there be a problem with their equipment? It might be useful to get an independant check to be sure. Especially if the fuel economy is improving.
Mark
Mark
12-19-2006, 03:38 PM
#44
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It is possible that the high flow cats are not getting hot enough to lower NOX. Some high flow cats are good from a performance aspect, yet not totally emission efficient.