87 240 wagon- Emissions (aarrgghhh)

[Harry von Zell]

Hi Guru's

Well, I replaced my CAT (aarrgghh) and my combustion is still a mess! My NOX is higher now than before the new CAT!

HC reading .79, Limit 2,25. - Way too low...
CO reading 1.48, Limit 23.74 - Way too low
NOX reading 11.60, Limit 3.25 - Way too HIGH

Car runs fine but the emissions don't lie. Somethin' ain't right.

Car has new wires plugs etc. Oil, Fluids clean and well maintained.

Any Ideas????

Thanks!
Harry

[Kmaniac in California USA]

First of all, there is no such thing as a measured emission being "too low". But if one is "too high" or "over the limit", you won't pass.

High NOX or Oxides of Nitrogen (Nitrous Oxide or NO2 is "Laughing Gas") is caused by high combustion chamber temperatures during ignition. The first place most people should look to correct this condition is the Exhaust Gas Recirculation (EGR) system. But guess what!?! You don't have an EGR system on your car! Neither does my mine! Now that we got that fact stated and out of the way, high NOX can be caused by advanced ignition timing or even a lean air/fuel mixture caused by a vacuum leak. Have you checked and adjusted your ignition timing? If the timing is good and you still have this problem, start looking for vacuum leaks. Look at all the vacuum hoses that connect to the intake manifold and replace all that look cracked or deteriorated. Also check the vacuum reservoir tank for the heater controls for cracks and leaks, too. You should even check the integrity of the intake manifold to head gasket, as well as the plastic tubes between the Air Mass Meter and the throttle body.

Now, the fuel injection system uses inputs from various sourses to adjust the fuel spray timing of the injectors. It measures the amount of air entering the engine with the Air Mass Meter (addition air from vacuum leaks will not be counted). It also takes input from the thottle position senser and the oxygen sensor and a special engine coolant sensor. Degradation of any one of these sensors could contribute to your problem, too. When was the last time you flushed the cooling system and changed the thermostat. A cold running engine can have an effect on the emission levels.

Changing your catalytic converter was a good move to lower your "unburned hydrocarbons" or HC. But this device only effects HC and has no effect on NOX or CO.

Anyway, start with the timing and vacuum leaks, then let us know what you find. By the way, which state is requiring this smog test? Here in California, they test us every two years and do so on a dynomometer. How about your state?

[Harry von Zell]

Will check the timing / vacuum related stuff first. Cooling system flushed yearly and is very clean. I also put in a new thermostat a month ago.

I am in RI. They also test emissions, via machine every 2 years.

Thanks and will report back.