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NOx failure, but everything else passed 700 1988

posted by  david hunter on  Tue Sep 22 11:37 CST 2009
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last visit: Mon Jun 30 22:10 CST 2014
[RELATED]

I hear you about FPR and O2 sensor not being the fault but why not look at your O2 output anyway. There is actually an LH2.2 test point connector along the passenger fender that can be monitored with an LED or any meter. When it flashes (goes alternately from 12V to ground) in a steady manner you have in theory achieved Stoicometric perfection. Of course you can also just look for the regular O2 sensoe output swings towards .1V and .9V with a digital meter. When I had my 88 740 and my daughter had an 87 240 it was my habit after a tune up or any work to tweek the MAF adjustment screw to achieve this. There is some info in the FAQ on the subject.

If the fuel mixture as measured by the O2 sensor is in line then maybe the NOX will come in line too. Just my thoughts.

I find it hard to believe that a minor (or major) exhaust leak can affect emission measurements at the arse. Then again maybe air is sucked into the exhaust stream in between exhaust strokes thereby upsetting the whole O2 sensor and cat chemical process, but that is just me rambling on.
--
David Hunter






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