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Discussion Starter #1
Hey guys,

I have a 94 525i automatic with 255,xxx miles on it. i took it to get smogged last month. The day before, I had changed the air filter and cleaned the MAF. My car failed. The NOx and HC was too high (see pic).


After the test, my CEL came on with the code 1221. I had the oxygen sensor replaced a little bit over a year ago, so it could pass smog (which it did).

Since then, I've changed the spark plugs, changed the oil, and fixed the valve cover gasket (had oil in the first spark plug housing). I put the "guarantee to pass" stuff in the tank with 91 gas. But due to some circumstances, I couldn't go smog it again.

So my questions are: is there anything else I can do to pass emissions? and is it alright to add "guarantee to pass" in again so soon?

And I heard that I should run lower octane gas, in older cars, when going for the smog. Is this true?
 

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Take it for a long drive before the smog test, longer than 30 minutes. I've heard it helps when everything is hot, but I haven't tried it myself.
 

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