91 300E Failed Smog Test by 5000% - PeachParts Mercedes-Benz Forum

JohnM. · #1 02-25-2010, 08:51 PM

Just took my daily driven 300E into get smog checked and got a concerning test result back. It failed both HC and CO, NOx was well within range. Car had a headgasket done 2 years ago at 120K, it has 165K now. Runs like a raped ape. No stumbles, no hesitations..it pulls from 0-80mph redlining every gear perfectly. I did a full ignition tune-up when I did the headgasket, along with a new EGR valve, smog pump. No smoke of anykind, ever. Never any rich smell except for very first startup on very cold days, which has always been the same.

The car gets awesome highway mileage on the last long trip I took (November)...got rougly 26mpg highway. Cruising up-grade the entire way from NM > CO at 80mph. Haven't done a mileage check in awhile, but will do one on the next full tank.

The readings are in (GPM - or Grams Per Million). For HC I got 3.2 when the limit is 1.5. For CO I got 118.57 when the limit is 20. NOx was .024 when limit is 3.5.

How could I have failed BOTH HC and CO so terribly if the car has absoultely no driveability issues?? I mean it has POWER all the time, never bogs down in any downshift/rpm situation..not even off the line.

I really have a feeling that the results are skewed and the test was NOT run correctly. They give you some % numbers on how bad you failed. Well my HC is 4579% higher than a comparable vehicle, while my CO is 1504% higher than it should. WTF? This can't be right? Or CAN it?

I checked the distributor cap and a few other things and even pulled a few spark plugs. Everything is normal. As it should be. As I would expect it to be. I'm thinking Catalytic Converter? If the goons at the testing place didn't screw up...

EDIT: Just for S&G I pulled up the emissions test from 2 years ago. Mileage is 123K. HC GPM was 1.6, limit 2.5. CO GPM is 15.6, limit 20. NOx 0.17, limit 6. CO is a tad bit high, which could have been indicating beginnings of the cat having reduced efficiency. But nothing has been done to engine in the last 2 years other than oil changes. By my super accurate seat of the pants meter, and the sheer amount of seat time in this one car...I can say the engine has lost no power in the last 2 years.