The car: 1994 C280 with 95,000 miles.

I just did my emissions certification on the car, as we have to do every two years. I passed, but when I compared the results to the test from two years ago, my HC ppm had increased dramatically. I had 17 ppm at idle and 33 ppm at 25 mph (I'm allowed up to 55 before I fail). Two years ago it was 0 and 0. What could cause such a large increase in HC? I brought the car into the test hot, having done a 20 mile run up the highway to heat it up for the test. I have a failed air pump, but as the car was started hot (it was on the test apparatus within 5 minutes of arriving) I don't think that has anything to do with it. I also intermittently get a code for a failed purge valve, but I just clean it out with Arthur Dalton's trick when I get the code.

Any ideas? If I increase the same amount in two years, I'll fail then. The plugs have less than 7,000 miles on them, as do the plug wires/boots and the MAF.

Thanks,

Jonathan

when did you last change the oil?

__________________
David S Poole
European Performance
Dallas, TX
4696880422

"Fortune favors the prepared mind"
1987 Mercedes Benz 420SEL
1988 Mercedes Benz 300TE (With new evaporator)
2000 Mercedes Benz C280
http://www.w108.org/gallery/albums/A...1159.thumb.jpg

The simple answer?
1. Ignition related items ( plugs, etc. )
2. oil consumption ( minute amounts ).
3. Catalytic converter degrading.
Remember you're reading parts per million.
Just because your numbers are up from 2 years ago does NOT mean they will continue to climb.

__________________
2007 C 230 Sport.

What grade of fuel have you been using?

David: the oil is changed religiously every three months, which amounts to about 1500 miles per oil change.

Manny: I refreshed all the ignition related items a little over a year ago, which amounts to about 7000 miles (plugs, wires and the three plungers below the coils). The car doesn't use any measurable amount of oil between oil changes. I hope that doesn't mean a catalytic converter, but with my luck it probably will. Its always the most expensive thing.

Rick: Premium fuel only, 91 Octane.

You worry too much.
If the car was tested again tomorrow, your HC's could be down ( or up ) 10, 20, 30 ppm.
How do I know,........I test exhaust emissions every day ( with my own 5-gas analyzer).

__________________
2007 C 230 Sport.

Is there any chance it could be the O2 sensor(s) "getting old"?

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

We have a 97 C280 with the inline 6, which have gone through several emission tests.
My experience is:
Cold -when I drove the car short trip (say, 10km) to test the HC was high.
Warm - when I drove it longer say 30km on highway to test the HC was always very low.
I believe the catalytic converter needs to warm up to perform well.



CF

I failed my inspection test,because my HC is reading 119 and HO% is reading 0.83, what can i do to fix that?

Year & model of car would help.

__________________
2007 C 230 Sport.

its a c280 mercedes 1995

Lots of questions:
1. What are your limits for HC and CO ?
2. When was the last time you did a really good tune-up?
3. Do you have a " Check Engine " light on ?
4. Has the Oxygen sensor ever been replaced ?
5. How is your fuel economy ?
6. How does the vehicle generally drive ?

__________________
2007 C 230 Sport.

1)none of the light are lighted up,
2)1 and a half year ago
3)no its not
4)No
5)prety good
6)perfectly

My vote:

O2 sensor.

__________________
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

mpolli

Based on the age of the car, I'm tempted to agree with you but, it bothers me that he does'nt have the Check Engine light on.
Possibly the catalytic converter " going south "?

__________________
2007 C 230 Sport.