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Emissions Fail - Advice welcome!

I took the car in for the emissions test earlier today and came out "failed". My NO levels look to be the issue. Was hoping some of you had already been down this path and could advise on items to try. All I have to pass is the 2-step testing procedure (ie. idle sniffer test and 3500rpms steady throttle) and not the roller/load test.

The car has a programmable EFI system, fairly stock motor and a high flow catalytic converter in the system. Recent plugs and plug wires.

To reduce NO emissions, do I want to lean the idle out to stoich and advance the timing?
Are there any additives members have had success with in the past?
Best,
John
Old 10-03-2009, 05:12 PM
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How far off are you? Post all of your results (HC, CO, NOx etc) along with the limit that you're allowed.

High NOx levels are caused by excessive combustion temperatures. Do whatever you can to bring them down (richer mixture, back off timing, etc). Carbon buildup is also a huge contributing factor. Dont get crazy with the adjustments, as doing so can cause you to fail other aspects of the test.
Old 10-03-2009, 06:56 PM
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emission

Good luck John...I am in the same boat out here in California...you can't fart without the DMV slapping a flam arrestor you you.
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Old 10-03-2009, 07:22 PM
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Daily,
Apologies, I got my problem area wrong - it was CO that was the issue, not NOx.

The emissions tester gave me an "aborted attempt" to give me the opportunity to clean it up before the actual test was performed.

The tech was not able to give me the 2-step results, but he ran the car on the rollers to show me where I was in relation to the targets.

Does the issue being CO give a different direction?
Thanks for the help.
Best,
John

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Originally Posted by DailyDriven'88 View Post
How far off are you? Post all of your results (HC, CO, NOx etc) along with the limit that you're allowed.

High NOx levels are caused by excessive combustion temperatures. Do whatever you can to bring them down (richer mixture, back off timing, etc). Carbon buildup is also a huge contributing factor. Dont get crazy with the adjustments, as doing so can cause you to fail other aspects of the test.
Old 10-03-2009, 08:03 PM
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Gotcha. High CO simply means you're running too rich, which is probably pretty normal on many 930's. You may also have a bit too much blow by, but I'll put my money on the mixture. Either case, lean it out and retest. Again, you may find that making adjustments can have a negative affect on other parts of the test, i.e. leaner mixtures can cause the NOx value to increase.
Old 10-03-2009, 08:29 PM
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First of all:

What car are we talking about? Which engine? What EFI? Do you have a lambda sensor and is it working? If you have a catalystic convertor you will probably have a lambda as well. Make sure that lambda is 1.0 during idle and 3500 RPM. If it's not (for example, if car runs rich) your CO values will be elevated.

We need full run on your figures to give you sound advice. The typical emission sniffer will give you CO, NOx, lambda and CO2. We need at least CO and lambda.



Car must run in closed loop during idle and 3500 steady throttle to deliver good CO values with catalystic converter.

Just having a cat and letting it run rich won't help.
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Old 10-04-2009, 05:56 AM
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Goran,
The motor is a stock 3.3L with the 1994 Turbo S M4P3-Option Camshafts. The ECU is a current generation AEM with a wideband lambda sensor running closed loop at idle.

Unfortunately, I was not able to get a readout on the numbers from the tech.

Car seems to run the smoothest at a 13ish AFR at idle, but I'll try leaning the mixture out to 14.7 and see where I come in. Thanks for the feedback.
Best,
John

Quote:
Originally Posted by beepbeep View Post
First of all:

What car are we talking about? Which engine? What EFI? Do you have a lambda sensor and is it working? If you have a catalystic convertor you will probably have a lambda as well. Make sure that lambda is 1.0 during idle and 3500 RPM. If it's not (for example, if car runs rich) your CO values will be elevated.

We need full run on your figures to give you sound advice. The typical emission sniffer will give you CO, NOx, lambda and CO2. We need at least CO and lambda.



Car must run in closed loop during idle and 3500 steady throttle to deliver good CO values with catalystic converter.

Just having a cat and letting it run rich won't help.
Old 10-04-2009, 06:27 PM
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A 14.7 afr will most definitely help from an emissions standpoint.
Old 10-05-2009, 01:02 AM
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Update - testing this morning. Another fail, but I got results this time. Can't believe how close I was to passing, and how much margin I had on most of the tested areas.

2500rpm Test
Reading Allowed Result
HC ppm 46 220 Pass
CO % 0.41 1.2 Pass
RPM 2479 2750 max
CO+CO2 15.7 6.0 min

IDLE rpm test
Reading Allowed Result
HC ppm 223 220 Fail
CO % 0.32 1.2 Pass
RPM 976 1250 max
CO+CO2 15.4 6.0 min

I think my problem is that idle oscillates slightly, causing AFR's to bounce a bit. Advanced timing some (to 22 adv), but the idle is a bit rougher... retard timing (to 10 adv) and it smooths out.

Since coming home, I leaned out the idle further to the 15's... this should help some... but do you think I should advance the timing at idle (which is supposed to result in a more complete burn but causes oscillation in the idle) or retard it (which smooths the idle out)?

Last edited by JBurer; 10-10-2009 at 12:40 PM.. Reason: can't format table!!
Old 10-10-2009, 12:35 PM
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Usually, you set up idle ignition timing quite low at idle RPM target (like 12 degrees @ 900 RPM) and raise it just below (like 18 degrees @ 800 RPM). As ignition is advanced, engine will pick up revs. So ignition advance at 800 RPM is used as guard against idle stalling.

Leaning out the mixture usually sends NOx values up but HC values down. If US emission laws don't care about lambda and NOx, you can lean out the idle until HC goes down. Also, you can raise idle RPM to 1000 revs or so (1250 seems to be max) in order to heat up the cat more.

Those tricks won't fly in Europe (they check NOx, lambda, HC and CO here) but might work in your case.
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Old 10-10-2009, 05:13 PM
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Quote:
Originally Posted by beepbeep View Post

Those tricks won't fly in Europe (they check NOx, lambda, HC and CO here) but might work in your case.
At what year do they stop looking at all that? My 79 is no longer tested here in GA.
Old 10-10-2009, 06:03 PM
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Goran,
That's a great tip on the ignition timing sub-idle - thanks!

They test here for NOx levels, but only OBDII and later cars (1996 onwards). I'm fortunate in that I only have to pass the 2-step test, which evidently doesn't test NOx and doesn't require a load test. If I had a newer car, this would be much more difficult.

Will let you know how I make out... planning to try this again tomorrow.
Best,
John

Quote:
Originally Posted by beepbeep View Post
Usually, you set up idle ignition timing quite low at idle RPM target (like 12 degrees @ 900 RPM) and raise it just below (like 18 degrees @ 800 RPM). As ignition is advanced, engine will pick up revs. So ignition advance at 800 RPM is used as guard against idle stalling.

Leaning out the mixture usually sends NOx values up but HC values down. If US emission laws don't care about lambda and NOx, you can lean out the idle until HC goes down. Also, you can raise idle RPM to 1000 revs or so (1250 seems to be max) in order to heat up the cat more.

Those tricks won't fly in Europe (they check NOx, lambda, HC and CO here) but might work in your case.
Old 10-10-2009, 06:27 PM
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Quote:
Originally Posted by DonE View Post
At what year do they stop looking at all that? My 79 is no longer tested here in GA.
Once the car is 25 years old it no longer has to be tested. http://www.cleanairforce.com/motorists/emissiontesting.

Two more years and my '87 won't be subjected to this...

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Old 10-10-2009, 07:15 PM
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Silly question, but is the motor hot when you're doing the test? Of the four times I've had my car smogged (in three different states), the only time it failed was the first, when I hadn't driven the car long enough prior to testing. I took it for about 15 minutes of full-throttle runs in the neighborhood, and then returned to pass with ease.
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Old 10-11-2009, 08:14 AM
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Quote:
Originally Posted by Noah930 View Post
Silly question, but is the motor hot when you're doing the test? Of the four times I've had my car smogged (in three different states), the only time it failed was the first, when I hadn't driven the car long enough prior to testing. I took it for about 15 minutes of full-throttle runs in the neighborhood, and then returned to pass with ease.
Good point, mine failed the first time I tested it and I think that may have been the issue. I just stopped by on the way home from my normal commute and failed.

The next time I ran it on the Interstate for 20 minutes and did some 2nd gear pulls just before I got to the station, passed with no adjustments or modifications. I also called the test station owner to make sure there wasn't a line.
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Old 10-11-2009, 08:28 AM
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Passed!

Retarded timing to 10, bumped the idle up to 1000rpms, leaned the AFR's out into the upper 15's and held revvs at 3,000rpms for a couple minutes prior to the test and she passed!
Thanks for the advice, guys!


Quote:
Originally Posted by Noah930 View Post
Silly question, but is the motor hot when you're doing the test? Of the four times I've had my car smogged (in three different states), the only time it failed was the first, when I hadn't driven the car long enough prior to testing. I took it for about 15 minutes of full-throttle runs in the neighborhood, and then returned to pass with ease.
Noah,
The motor was up to temp, but not *hot* like after several WOT runs. Think I mimicked most of that with the standing revvs, thought. When I have to do this again next year I will definitely add a few WOT runs to my test prep... because, if for no other reason, it's fun!
Old 10-11-2009, 04:55 PM
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Quote:
Originally Posted by beepbeep View Post
Usually, you set up idle ignition timing quite low at idle RPM target (like 12 degrees @ 900 RPM) and raise it just below (like 18 degrees @ 800 RPM). As ignition is advanced, engine will pick up revs. So ignition advance at 800 RPM is used as guard against idle stalling.

Leaning out the mixture usually sends NOx values up but HC values down. If US emission laws don't care about lambda and NOx, you can lean out the idle until HC goes down. Also, you can raise idle RPM to 1000 revs or so (1250 seems to be max) in order to heat up the cat more.

Those tricks won't fly in Europe (they check NOx, lambda, HC and CO here) but might work in your case.
Hej Göran Dont forget to mention: If possible add Ethanol in the gasoline
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Old 10-26-2009, 10:31 AM
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