Help - Failed Emissions Test - PeachParts Mercedes-Benz Forum

wbrian63 · #1 11-11-2006, 12:17 PM

'92 300SE - went for emissions/safety inspection this AM.

Car @ full operating temperature - no misses at idle.

Failed in spectacular fashion in both low & high speed tests:
High speed results
Pollutant / Standard / Current / Result
HC (PPM) / 120 / 326 / FAIL (no wonder the exhaust "stinks")
CO (%) / .67 / 7.98 / FAIL
CO2 (%) / / 9.9
O2 (%) / / 0.0
NOx (PPM) / 848 / 25
Dilution (%) / >6 / 17.9

Low speed results

Pollutant / Standard / Current / Result
HC (PPM) / 124 / 326 / FAIL
CO (%) / .69 / 7.73 / FAIL
CO2 (%) / / 10.0
O2 (%) / / 0.0
NOx (PPM) / 848 / 46
Dilution (%) / >6 / 17.7

One thing I noticed is the vaccuum hose that attaches to the air pump had come detached. Can't seem to get that sucker to stay put - isn't vaccuum in that hose? Seems like it keeps blowing off.

The other peculiar item is that the state computer system (TX) reports that the engine size on the car is 3000CC, not 3200CC. Smaller motors make less emissions (in general terms), so I'm wondering if the standard values are too low for the car. I expect that once the problem causing all the unburned fuel is located that the #'s will fall well within standards.

Anyway - unless I miss my guess, without the air pump, there's not enough air in the exhaust to allow the catalysts to properly scrub the gasses.

I'll check for codes on the computers and pull the plugs for an inspection and report results.

Any suggestions for where to start looking, or for why that pesky little hose won't stay attached to the air pump would be appreciated.

Regards

Moneypit SEL · #2 11-12-2006, 01:33 AM

Your fuel mixture (CO) is way rich. Fix that first. I'd start by looking at the O2 sensor. Once you get CO under control, your HC numbers should come down. The catalytic converter may start working again, or it may not. A good hard run on the highway after getting the CO handled might just wake the cat up.

Nate · #3 11-12-2006, 01:41 AM

buy the sticker for $100, or make sure the car's good and hot before u take it in...

Any car can pass an emissions test
~Nate

wbrian63 · #4 11-12-2006, 11:19 AM

First - the hose I referred to earlier does not go directly to the air pump, but rather to the valve at the back of the air pump. I started the car up and surprise, surprise, surprise (in my best Gomer Pyle) - there's positive air pressure coming out of the nipple where the vaccuum hose should attach. Looks like a ruptured diaphragm on the valve - I'll replace that Monday.

Moneypit SEL - thanks for your insight - I kinda figured that the CO and HC were related. I still need to pull codes and see what the computer is mad about.

Nate - I strongly suspect that's how the car got the last sticker, since the motor is new and it's been less than 2K since it was installed. The line I refer to above was disconnected then, too - so likely the valve was faulty when the motor was exchanged.

As for buying the sticker - down here in Texas they lock people in jail for doing that - if you get caught. Based on your signature - referring to your age, you're not old enough to have experienced life before emissions control. I'm 43 and when I started driving in the 70's, few cars even had so much as a catalytic converter. Many was the time I'd sit at a stoplight next to a mosquito killer (LOTS of blue smoke) and right behind a car running SO rich that the exhaust looked like it was coming from a diesel. When manufacturers started putting emission controls on, the designs were so bad and sapped so much of what pitiful amounts of power cars of the 70's and early 80's had that many people defeated them. I have a '66 Cadillac with a 7 litre motor (429CI) that makes 340net horsepower - but it does it with 10.5:1 compression and a 4BBL carburetor that nets 8mpg city 12/highway. That's 48.5 hp/litre of displacement. The Benz makes 228 hp from 3.2 litres (71.25 hp/litre) and should get 25+ mpg on the highway - but not if I'm dumping a TON of gas down the pipe.

It's a shame that we had to endure the early years of emissions, but I like where we are now. Here in Houston, we face mandatory reduction in the max speed limits allowed on our freeways - not from a safety issue (most were designed and built for '60's cars - and 70mph), but because our air quality doesn't meet federal standards, and to keep the federal highway dollars we so desperately need we must comply. In my 28+ years of driving, I've logged close to 750,000 miles - and most of that on the streets in and around Houston - I don't want the next 750,000 miles to happen and 40mph, so I want CLEAN AIR.

Sorry for highjacking my own thread - but I'll fix the car and enjoy the good mileage and clean air.

Tomguy · #5 11-12-2006, 12:18 PM

Correct me if I'm wrong, but doesn't Houston now have the title of "Worst smog in the US"?

The smog pump itself wouldn't make nearly that much of a difference in your emmissions. Even a car with no cat has lower CO than that. You're dumping WAY too much gas into the engine. Get a new O2 sensor, and your plugs are almost surely fouled black by now - new plugs wouldn't hurt either. Check your injectors for dripping or uneven spray. Check the cap and rotor as well. Lastly, run a large bottle of injector cleaner in half a tank of gas and "Drive it like you stole it" on the highway for a good 10-15 minutes to clean out all the carbon deposits you almost certianly have on your valves and piston faces.

manny · #6 11-12-2006, 12:24 PM

Quote:

Originally Posted by Tomguy

Correct me if I'm wrong, but doesn't Houston now have the title of "Worst smog in the US"?

Hmmmmm, let me see, 80 % of airpollutants are emitted by industry, 20 % or less by vehicles.
Ahhhhh, who cares, let's beat all the carowners over the head with a big stick, because they are easy targets.

Tomguy · #7 11-12-2006, 12:30 PM

Not to get off topic, but I was NOT blaming vehicles at ALL. I would blame the repealing of the Clean Air Act LONG before I'd blame a vehicle...

Do you see what vehicle I have? I'd hardly say the 4.5 is environmentally friendly. But a year of running a 4.5 non-stop still won't touch an hour's worth of emmissions from a refinery!

wbrian63 · #8 11-13-2006, 08:25 AM

pulled codes from computers
Fuel Injection - code 1 (no issues) returned

Base Module - host of errors, all pointing to blown fuses (F1, F2 and F3) in computer module. Pulled cover, checked fuses - all OK. Cleared codes. (Checking the list of items fed from F1, F2, & F3 it would seem likely if all 3 fuses were blown that I'd have a no-start situation)

EA/CC returned several codes, only one of which was listed as a valid code for that module. Cleared codes.

Pulled spark plug from front-most cylinder. Plug smells strongly of gasoline but is not fouled or terribly black.

From what I could gather on AllData, the O2 sensor can only be diagnosed with a "cycle tester" (not sure if I'm right on the name).

I thought that the DM (Diagnostic Module) which is referred to in AllData would have been the ticket to see what's what, but the pin in the X11 socket identified for it in AllData doesn't have a connector, so I guess my car doesn't have that module. (It's a very early '92 - vin ends in 023154).

I guess I'll try replacing the O2 sensor - likely it's the original one as the car only has 100k miles on it.

BTW, the plugs were those nasty Bosch platinum 4 electrode jobbies. Seems like I remember reading that those are best used to line the bottom of an ash can (at least for our cars) - what plugs should I be running in my M104?

Thanks for all the help thus far. PLEASE no more posts about Houston's air - they're not related to my problem. (Although with the gasses my car is producing, I'm surely a contributor to the situation.)