1996 BMW Z3 SMOG FAILURE - CALIFORNIA

  • Tiny
  • cdm_
  • 1996 BMW Z3

Engine Performance problem
1996 BMW Z3 4 cyl Two Wheel Drive Manual 111000 miles

passed the following:

Visual
Functional
CO2
O2
HC
CO
(I tested extremely low for all of the above).

I failed NO (PPM):

15 mph (1982 RPM): 459 (allowed) 1065 (tested)
25 mph (1997 RPM): 746 (allowed) 278 (tested)

My first thought was cats, but the disparity between tested scores vs. Tested RPM has me thinking something else. O2? ECV?

Thanks in advance for the input.

By the way, drove on the freeway at 3500 rpm for an hour prior to the test.
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Tuesday, July 7th, 2009 AT 8:18 PM

1 Answer

  • Tiny
  • Dr. Hagerty
  • Expert
  • 9,717 posts

NOX can often be high due to carbon deposits, I have had success with high NOX cars by running water in the intake. It will clean out the carbon and lower the emissions. Do it slowly, it takes about a half gallon.

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Wednesday, July 8th, 2009 AT 4:35 AM

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