Emmisions test

[Guest alex_houston]

I have been working on a car I bought from the local police auction. It runs strong, no smoke and seems great in every way.

Today it failed the emmisions test. Allowable high speed Nox is 848ppm but failed at 2687. Low speed allowable 937 but failed at 2437.

Is anyone out there that knows what can be wrong?

Please help! Thanks

[shoreice]

How long since it's been driven? May just need a "Cosby Tune Up" and test while still hot. LOL Kenny

[Guest alex_houston]

I don't know know when last driven. Has all new gas and plugs. What is a "Cosby tune up"?

[Texan]

Hi Alex, it may be the type of gas that has been used in it, gasoline is like a hamburger, different companies order gasoline with little or no additives and some order their gasoline with quality additives. Convenience stores order gasoline with few additives, most major brands, Chevron, Shell, Texaco use better additives. Try running a few tanks of fuel with gasoline from a name brand station and buy some additives at a parts store. It may solve your problem.

Also, check your catalytic converter, it may be part of your problem.

Texan

[Guest alex_houston]

Unfortunately I cannot drive it around without an inspection sticker. It is hard to run out a tank of gas sitting in the driveway. It was filled up with Shell Premium and a can of "guarantee to pass inspection" additive was added.

I am quite capable working on most any part of a car and I do more than my share but this emmision stuff I have very little knowledge. I was thinking Cat Converter, oxy sensor and possibly mass air flow sensor. How do I get a Cat converter checked other than just changing it? I have never heard of any test for them? Have I missed something?

[manikmekanik]

If the Cat is plugged, it may cause failure of the digital EGR valve, or gasket.

This can be diagnosed by testing the exhaust back pressure, if too high, cat is restricted.

Generally the 3800 will pass emmissions without tuning, if the cat is operating properly.

Also, check for leaky or bad fuel injectors, or faulty fuel pressure regulator. A regulator gone wild can cause injectors to leak with time.

[cal55]

I would change the O2 sensor too, they're only about a $15.00 item and easy to change. I had a 92 LeSabre with the same engine, the 3800 and it failed due to a bad O2 sensor.

Joe

[shoreice]

"Cosby tune up" is 100MPH in second gear to blow the gunk out. To be performed on "any side Street". Really tho, try a run down the freeway to clear the gunk out and get the cat hot. Here in NJ we get big red rejected stickers on the windshield from the state DMV, gives us 45 days to fix and retest after failing yearly inspection.

[2seater]

Usually excess NOX is a byproduct of high combustion temperatures, and the EGR is used to reduce and dilute the fuel mix. Not that other things don't effect it, and the suggestions are good, but the EGR primary function is NOX reduction. Is the low speed test at idle? If so the EGR isn't in play, but I wonder if there is a passage plugged if you get no malfunction codes? Just a thought.