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Old 12-28-2001, 09:15 PM
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Join Date: Oct 2001
Location: Currently assigned @ Travis AFB, CA
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Unhappy California 88 260E failed Maryland Emissions

Just went and fail the Maryland’s emissions test on my 88 260E (California model), this was the first time testing for this car in this state. Since I brought the car last year from a friend in California I hadn’t done much to it except change the Oil, ATF and Rear Differential oil (all Redline products). I did recall him saying it failed the California “Smog Test” the first time but pass after the same shop did some things to it. Well anyways the following are my results:

1. Hydrocarbons-FAIL: State Standards-2.0000 GPM, My results 3.2803 GPM
2. Carbon Monoxide-PASS: State Standards-30.0000 GPM, My results 26.5344 GPM
3. Oxides of Nitrogen-FAIL: State Standards-3.0000 GPM, My results 7.3888 GPM
4. Carbon Dioxide-N/A: State Standards-N/A, My results 379.1985 GPM

They gave me a brochure of things that maybe causing the problems. My question to youall is for this particular model is there anything that can cause these readings?

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Old 12-28-2001, 09:24 PM
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I used to live in Maryland. My first advice is GET OUT! Failing that, the most common reason a car will fail a smog test is that the engine is not fully warmed up. Put some new spark plugs in the car, then drive it, hard, for at least 20 minutes immediately before the smog test.

Let us know how that turns out. Once you've passed the smog, you get to deal with Marylands' rather anal vehicle inspection.
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Old 12-29-2001, 12:09 AM
Mike Murrell's Avatar
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Join Date: Feb 2000
Posts: 2,141
Mallory gave the best advice...make sure the engine is fully warmed up. Find out when the smog test facility opens up for business. Drive around for a good while and get there just before they open. You want to be the first guy in line.

Mallory mentioned fresh plugs. Also consider the condition of the air filter. If it's dirty, your mixture will be richer...not good.

Some say that premium gas reads cleaner in these emissions tests. I do not know this to be true. Perhaps someone with some knowledge in this area will confirm/shoot down this idea.

Are your plug wires good?...rotor..distributor cap?

Then there's the O2 sensor and last, but not least the catalytic converter. If it's hosed, kiss it all good-bye.

I don't know what your timeline is, but it might not hurt to run a tankful of Techron or BG-44K thru before you return for round 2. I saw some snake oil at Pep Boys awhile back(don't recall the name), but it clearly indicated it was for helping you pass an emissions test....somebody elses version of Techron.

Good luck.
Mike Murrell
1991 300-SEL - Model 126
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Old 12-29-2001, 01:33 AM
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If you think your cat is borderline, then instead of a 20 minute run, make it an hour or more. That'll get the cat good and hot, which might push a borderline cat into an OK reading.
Mike Tangas
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Old 12-29-2001, 03:48 AM
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Location: Malaysia
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260s run well on hot engines, as compared to many other models. It is more particularly sensitive to any imbalances in the engine management, i.e. CO level adjustment, plugs, oil, etc ... that may have a bearing on others.

Is there anyway of going through the checklist on your brochure and take the car out for a test run before going in for the test proper? Surely some workshops around your area may have the instruments ready?

Singapore has an equally stringent test for older vehicles and I used to reduce the CO mixture in my brother's 123 200 just to pass the emission test. And then re-tune the levels for optimum performance.
... Kerry

126 tailed by a 203, 129 leading the pack.
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Old 12-29-2001, 07:29 AM
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The NO readings are way out of whack. If i remember way back when I took my emission class this is controlled by the EGR valve. (Cylinder combustion temp too high.) The EGR cools the combustion chamber. This valve opens under acceleration and allows the burnt exhaust gas to pass into the combustion chamber and be re-burn and also lowers the temp of the cylinder (under 5000 deg) . The high temp (over 5000 deg) adds extra oxygen to the nitrates. It's been 20 years I might be remembering it wrong. One of you young tech's correct me if that the case
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Old 12-29-2001, 09:47 AM
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Join Date: Apr 2001
Location: Joliet Illinois
Posts: 309
Failed Emissions

I also have a '88 260e that failed emissions for the previous owner. He ended up having the cat repacked. Apparently that is possible with these cars. I have also learned that worn valve guides and valve stem seals cause oil to enter and damage the cat which could be the cause of your problem. My car passed after the cat was repacked.
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Old 12-29-2001, 10:15 AM
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Join Date: Aug 2001
Location: Northern Virginia
Posts: 2,911
You appear to be pretty far out. It may indeed be the catalytic converter that needs replacement.

However, if you want to try again, I usually tell my friends that live in the socialist zones of the country the following:

1) Change oil immediately before the test. Use an additive such as STP oil treatment that further thickens the oil. This sharply reduces burning oil.

2) Start using premium gas for a tank or two before the test. Premium is cleaner and the refiners take better care in handling it. Regular is used to flush storage tanks out when they're being cleaned.

3) New spark plugs was a good suggestion.

4) Try to make sure there are no loose vacuum hoses that would mess up the fuel mixture by sucking in air.

Like other people are saying, you probably are looking at something more expensive to fix. But the test may be worth another try if the oil was old, the spark plugs are old, the EGR valve is clogged, and the fuel is dirty.

Good Luck -

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Old 12-29-2001, 07:15 PM
Ali Al-Chalabi's Avatar
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Join Date: Nov 2000
Location: Knoxville, TN
Posts: 1,837
The cat plays a large part in reducing Nitrous Oxides in the exhaust. As suggested get it as hot as possible and if it still fails, it will need to be replaced.

Also, when was the last time the O2 sensor was replaced, I believe it is possible for a bad one to cause the hydrocarbon reading to be too high due to a rich mixture.

Good luck.
Ali Al-Chalabi

2001 CLK55
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Old 12-29-2001, 09:04 PM
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Location: San Francisco, CA
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California 88 260E failed Maryland Emissions

If you suspect your engine may need valve stem seals ... try changing the oil with Valvoline MaxLife. It has done wonders for my '91 300E with 166K miles.
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Old 12-30-2001, 11:16 AM
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Join Date: Jul 2000
Posts: 638
emissions values

Always before emissions tests run at least one tank of gas with TECHRON added. Change the oil. If the car is misfiring at all--fix that problem first no way it will pass. Run the car HARD for an hour or so to really 'exercise' the catalyst and spark plugs, and arrive for the test HOT. This also helps the O2 sensor out. It if is bad or weak, you will get this type of bad emissions numbers. The mixture to the catalyst has to be kept just right for it to work.

Your car results are not encouraging the NOx is way high which indicates either plugged exhaust recirculation passages/valve or catalyst that is dead. The hydrocarbons are also high but that can be caused by dirty oil.

Change the air filter also.
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