__________________
-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi

There were a couple of threads on this subject recently, although I don't think either one actually went to a conclusion unfortunately. Anyway, it sounds like an O2 sensor. There are threads telling how to test that.
Mike

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

Which car is this on, the 300E? If so, how old is the O2 sensor?

__________________
Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

This is on the C280. The car was recently purchased so I don't know how old the 02 sensor is.

I'm going to run some tests (pull codes, etc.), change plugs and oil and see what I can turn up.

I don't understand though why HC's would jump so high when reducing NOx.

Thanks for the replies.

__________________
-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi

If it is the O2 sensor, it should store a fault code. That car has 2 O2 sensors. What did you do to reduce the NOx, replace the cat?

__________________
Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

Typicly what causes high NOx readings...which on a Gas engine is a lean misture indication. and therefor high combustion temps.....fattening up the mixture to reduce that will rais the HC's .......also a bad cat will give horrible HC's.


How many miles are on the engine? I would run a can of BG products BG44K......thats the best injector and combustion chamber cleaner I have personally used.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Perplexing. Repairing a clogged EGR tube should not upset the mixture and cause a rich condition, which is indicated by the numbers. Regardless of EGR, the lamda system should maintain a stoiciometric mixture, and your HC and CO emissions should not have changed signficantly.

As stated, check codes and O2 sensor function. Did something inadvertantly get disconnected or reconnected incorrectly while you were working on the EGR tube?

Duke