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Steve, BMW Expert
Category: BMW
Satisfied Customers: 24187
Experience:  BMW Expert
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1997 BMW Z3 1.9 Failed smog ck. 46,000 original miles ONLY,

Customer Question

1997 BMW Z3 1.9 Failed smog ck. 46,000 original miles ONLY, nothing modified-stock only.
NO ENGINGE LIGHT and NO codes returned on Peake analyzer. NOx too high... by a couple hundred points.
I have taken good care of this car, oil and filter etc. Not driven hard. Smog guy was totally confused with no codes on his machine...Drove car 30 miles before taking it in the second time so engine was fully hot. Took it to 2 different stations for the smog checks.
What do you think... would catalytic converters go bad at 46000 miles? If they were bad would not a code be returned by the computer?
Submitted: 2 years ago.
Category: BMW
Expert:  Steve replied 2 years ago.

it is possible that CATs could be bad, but not terribly likely

Expert:  Steve replied 2 years ago.

more likely than a bad cat would be a lean fuel mixture causing the high NO

Expert:  Steve replied 2 years ago.

what sets a code or warning light vs. what a smog check considers out of spec are totally different, so the fact there are no codes stored should not have been a surprise to the smog guy. If there were codes you would fail automatically immediately. The purse of the actual exhaust monitoring part of a smog test is to find excess emissions that do not set codes.

Expert:  Steve replied 2 years ago.

Please let me know if you have further questions. Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you.