My 1985 740 GLE failed it's emmisions test last week. The CO levels were three times the legal limit, and the HC levels were pretty high also. Strangely enough, the NOx emissions were safely in spec. At any rate, they failed me for ignition timing also (error "B06"). I am assuming due to the large amounts of Carbon Monoxide that my Catalytic Converter is dead...could that be caused by my ignition timing being bad? How do I adjust the ignition timing in this car? I hear that it is controlled by the onboard computer

By the way, this car passed the emissions testing last year with flying colors.

Thank you in advance,

Calista

You gotta find out why your car is running so rich (or not fully combusting)

What the f*ck? They check for engine timing, error codes? That's like a full body cavity search...bendover while I lube the glove....what no lube!!???

However the timing thing is a clue...way retarded?

Your car has problems. Diagnose the problems, not the symptoms. The cat may still be alive or now dead because of the problems.....

Can't tell you what is wrong, but maybe help explain the numbers. CO is a measurement of how complete the combustion process is. Ideally every carbon molecule will combine with two oxygen molecules to make CO2. High CO shows that the process has not been complete, and can indicate a lack of oxygen to the process. High HC is unburned gas. Pure and simply, waste. You can expect to find it along with the high CO reading. An extreme condition will produce black smoke. NOX is formed at the other end of the combustion spectrum, when there is such a hot reaction that oxygen combines with nitrogen, the most plentiful component of air. This is usually found in a lean mixture situation.

Your problem can be caused by a number of things, the simplest being a broken or missing thermostat, or performing the test on a cold motor. Others have the experience to help you troubleshoot the rest, but don't be so surprised at your test numbers. They reflect the constancy of our physical world.