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Old 02-09-2005, 04:48 AM
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pmizell pmizell is offline
Benz Zealot
Join Date: Jun 2001
Location: Houston, Texas
Posts: 838
Angry Low HC/CO/CO2, High NOx/O2 (failed TX emissions)

Readings: Standard Current

HC (ppm) 114----22 ====> pass
CO (%) 0.63---0.01 ====> pass
NOx(ppm) 796----2405 ====> fail!

Tested but not graded:

CO2(%) 13.2 (seems almost perfect)
O2(%) 20.8 (very high?)

I understand high NOx readings are caused by an unusually rich air/fuel mixture setting, high combustion temps and/or malfunctioning EGR.

I'm wondering if a 'dragging' parking brake would cause such high NOx readings. (high combustion temp) It sometimes doesn't release all the way on my car and the inspector did test the brake. It's since been adjusted and the engine operating temps are otherwise normal.

The car is a new to me '94 C280 and I've read about the EGR tube clogging problems. It has 101,000 miles on the clock. The very low CO and HC makes me believe I need to richen the mixture -- OR could extra load from a dragging parking brake cause this??

As far as driveability, the engine runs and idles superbly so this emissions failure has got me wondering.

Any insight would be very much appreciated!
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi
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