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Old 03-12-2003, 04:50 PM
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300E Emissions Test Results


Can anyone tell me what can be said of the following results:

HC 0.542 Standard is .455
CO 2.704 Standard is 3.419
CO2 330.0 No Standard listed

State of IL

Car: 1990 300E 134K miles.

Just thought something might be told from the results. Seems to me that the car is running rich.


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Old 03-12-2003, 06:09 PM
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There is nothing major wrong with your car. Was your cat good and hot? This is the most important thing. Unless the cat has been replaced, I would say it is down to 10-15% efficiency.
Run some injector cleaner though it, run at high speed for 20-30 miles. Gas up with new before retest.
Check plugs, gap, condition. Check wires, resistance. RorR air filter. check for vacuum leaks before & after the intake. If possible scope the O2 for sluggish response.Check timing.Check coil that its hot enough. Lastly, check EGR ( if equipt) for flow constrictions. ie carbon build up.

Good Luck.
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Old 03-12-2003, 10:51 PM
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I passed the test in spite of a fault code for the Oxygen Sensor. Go figure.

The Cat was pretty hot in that I drove for about 20 minutes before the test.

Perhaps a failing 02 sensor might have caused the high HC level?

I've changed the plugs about 3000 miles ago and the old ones were perfect -- light brown in color.

Wires were done about two years ago.

I plan on changing the oil this weekend and running a couple of bottles of Techron before the change. The injectors are fairly new but cleaning them can't hurt.


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Old 03-13-2003, 10:32 AM
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Join Date: Jul 2001
Location: SoCal
Posts: 1,303
If your O2 sensor has failed, you will be running open-loop. Likely your pre-cat HC emissions are very high, and the cat is sucking it all up, consuming its 9 lives rapidly. Save the cat and fix the problem - O2 sensors are much cheaper.

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Old 03-13-2003, 10:49 AM
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Hi Steve,

Thanks for your reply.

I agree with you -- I forgot to mention that I'll be replacing the sensor this weekend too.

I'd rather not have to replace the cat:-)


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