Snookered by the emissions police--Looking for help/background info

[79er]

I have a '92 Legacy wagon that passed Colorado emissions in 2004 and 2006 and is due for another sniffer test this month. Because the standard changed TODAY from 20 GPM for carbon monoxide to 15 GPM, I see a likely failure--the state conveniently printed out out the values of each component on the earlier tests, and CO measured 16.7 and 16.9 on earlier tests (the real bummer is if I had a '91 or earlier model the standard remained at 20). HC and NOx limits were also reduced as of today, but the previous tests suggest I should have no problem (HC emissions were .7-.71 with the current fail value of 1.5; NOx was 1.0 and .6 with the current fail value of 3.5). So everything seems healthy, just a tad rich as evidenced by the CO numbers (if only I'd done the emissions test last week!).

 

As to a fix, how much effect will replacement of the O2 sensor have if HC and NOx are well within limits? Is CO the only component the O2 sensor regulates? or is the problem with the mass air flow sensor--do they get dirty or collect debris that could throw off the air/fuel ratio by a small amount? If so, can anyone recommend a cleaning procedure? Or other possible fixes for this slightly rich condiiton? Would appreciate if anybody with the same model could give me a baseline as to what typical CO values are for this engine. Any help appreciated--hate to spend big bucks for such a small deviation, especially since it was an "OK" value yesterday.

 

Woody

[hankosolder2]

I have a '92 Legacy wagon that passed Colorado emissions in 2004 and 2006 and is due for another sniffer test this month. Because the standard changed TODAY from 20 GPM for carbon monoxide to 15 GPM, I see a likely failure--the state conveniently printed out out the values of each component on the earlier tests, and CO measured 16.7 and 16.9 on earlier tests (the real bummer is if I had a '91 or earlier model the standard remained at 20). HC and NOx limits were also reduced as of today, but the previous tests suggest I should have no problem (HC emissions were .7-.71 with the current fail value of 1.5; NOx was 1.0 and .6 with the current fail value of 3.5). So everything seems healthy, just a tad rich as evidenced by the CO numbers (if only I'd done the emissions test last week!).

 

As to a fix, how much effect will replacement of the O2 sensor have if HC and NOx are well within limits? Is CO the only component the O2 sensor regulates? or is the problem with the mass air flow sensor--do they get dirty or collect debris that could throw off the air/fuel ratio by a small amount? If so, can anyone recommend a cleaning procedure? Or other possible fixes for this slightly rich condiiton? Would appreciate if anybody with the same model could give me a baseline as to what typical CO values are for this engine. Any help appreciated--hate to spend big bucks for such a small deviation, especially since it was an "OK" value yesterday.

 

Woody

 

 

If you use a highly oxygenated fuel, it may help. Why not add a couple of cans of that "guaranteed to pass emmisions" fuel additive to the tank? I think it's mostly alcohol, and will effectively slightly lean the car out. (Unless the 02 sensor compensates.)

Also, bear in mind that the same car will often test better and worse with the exact same test procedure; there's a good chance that you might pass anyway.

 

A fresh 02 sensor is not a bad idea. HC is unburned fuel (basically misfiring or gross over richness.) NoX relates to the combustion temperatures and will be WORSE (i.e. increase) with leaner mixture. So, the fact that your HC and NOX levels are within limits doesn't necessarily mean that you're not running fairly rich.

 

Make sure the coolant temp sensor's resistance is within specs at operating temperature. The Haynes manual has a chart and I think someone has also posted values here- search.

 

Good luck- let us know what happens.

 

Nathan

[four-fleet-feet]

I've had some marginal tests on past vehicles, and here's my 2 cents'.

 

Make sure your car is warmed up! Give it a good drive on the freeway (at least 10 miles if over 60 degrees, better double that if it's colder). Cross-town is not as good, you need to get it out on a cruise. Don't turn it off for any reason once you're at the station. Pick a line without a huge backup - the longer you idle, the more chance you'll have to fail.

 

If you have a locking gas cap, take the key for it off your keyring so you can hand the tester the key without stopping your car.

 

The liquid 'pass your emissions' stuff really does work on a marginal vehicle, but also check your plugs and wires (change them if you like), toss on a new air filter and PCV whether you do the plugs and wires or not.

 

Note the liquid stuff usually takes a half tank of gas to work, or more, depending on brand. Buy it ASAP if you intend to use it, it's not for day-of-test addition. Read the bottle and follow the instructions.

 

Note: if you normally keep a low fuel tank, or buy cheap gas, it might mean you'll need a fuel filter in a little while, as it will move crud about - better out of your car than in, IMHO.

[idosubaru]

how old are your plugs and wires? (are they OEM?) replace your plugs and wires and i bet you pass just fine.

 

happens all the time...fail....replace plugs/wires....pass.

 

which means one of two things...the plugs/wires make a significant difference or the tests have quite a variation.

[79er]

Just to follow up, for anyone facing a similar circumstance, I was able to successfully pass Colorado emissions. It would have been nice to know what action(s) had the greatest effect, but at $25 a pop for repeat testing, I just decided to do everything that was inexpensive, plus a new O2 sensor (not so inexpensive!) that might have an effect. The "before" figures are in my original post, and the test results after a new O2 sensor and other minor fixes were as follows: HC -0.1187 ((17% of earlier value), CO - 4.3302 (25% of earlier value), NOx -0.5327 (88% of earlier value)--these figures are a "grams per mile" value that Colorado seems to prefer rather than a percentage value. (Fail values are 1.5 GPM for HC, 15.0 GPM for CO, and 3.5 GPM for NOx, so all values are now well under the fail threshold).

 

As for the measures I took to get this improvement, besides a Subaru O2 sensor, I ran a pint of injector cleaner (valvoline) through the engine in one full tank of gas, replaced the air cleaner filter (though the existing one was not at all plugged up and had about 15,000 miles of use), replaced the spark plugs (plug wires appeared in good shape and only two years old), filled the gas tank the day before the test to 14 gallons and topped off with about 2 gallons E-85 which I estimated should make about 12% ethanol content, changed engine oil and filter, drove for about 7 miles at highway speeds (@4,000 rpm) before turning in to the emissions test facility, and earlier also cleaned the air sensor and the throttle body--one of the Lexus forums has an interesting thread on this--you can check it at the following URL:

 

http://www.clublexus.com/forums/showthread.php?t=345147

 

I was quite gratified with the large improvement in HC and CO readings and hope for not too much of an increase 50,000 miles from now (the engine currently has 158,000 on the clock) if I take the same measures for future tests.

 

Woody

[four-fleet-feet]

Hooray! Glad you passed.

 

That link to clublexus is awesome. I've gotta do that!

 

Big :clap: Thank You! :clap: for posting it for us.

 

(figures that post was from another Seattleite - we don't buy nuthin' new if we can help it... not quite as bad as an Alaskan, but we're pretty close)

[nipper]

were the standards always loose, and they just tightened them to the federal standard or somehting else?

 

It's highly unusual for them to change the specs for an older car.

[CNY_Dave]

were the standards always loose, and they just tightened them to the federal standard or somehting else?

 

It's highly unusual for them to change the specs for an older car.

 

In cali they do that to force older cars off the road.

 

 

Dave

[79er]

In cali they do that to force older cars off the road.

 

 

Dave

 

Exactly the logic in Colorado--according to the article in a local paper (mostly a rewrite of the State's press release, I'm sure) the expectation was to flunk about 31,000 vehicles with the tightened standard. Standards for 1981 and vehicles have roughly been cut to half the previously allowable emissions, e.g., for my old '75 pickup HC is cut from 1200 to 600, CO from 6 to 3.5.

[nipper]

Exactly the logic in Colorado--according to the article in a local paper (mostly a rewrite of the State's press release, I'm sure) the expectation was to flunk about 31,000 vehicles with the tightened standard. Standards for 1981 and vehicles have roughly been cut to half the previously allowable emissions, e.g., for my old '75 pickup HC is cut from 1200 to 600, CO from 6 to 3.5.

 

i did not know nor think they could make the emissions tighter then what they were for that year the car was made in. i wonder if anyone has tested this in a court?

[johnceggleston]

i did not know nor think they could make the emissions tighter then what they were for that year the car was made in. i wonder if anyone has tested this in a court?

 

generally, i would have agreed with you since that has always been the way it was in the building industry. if you met the code when you built the house, then you were 'grandfathered' in for any code updates.

 

but, they are in effect outlawing all TVs with rabbit ears. they are giving you a way to still use them, but ...

[nipper]

generally, i would have agreed with you since that has always been the way it was in the building industry. if you met the code when you built the house, then you were 'grandfathered' in for any code updates.

 

but, they are in effect outlawing all TVs with rabbit ears. they are giving you a way to still use them, but ...

 

Well the rabbit ears still work, its the part between the rabbit ears and the TV that wont.

 

i know NY stays with the year of mfg, as time does a better job of forcing old cars off the road then does forced emissions failures. And old cars that are still on the road usually pass with flying colors, as they are prized posessions.