Hi,

I just purchased a 1993 300e 2.8 with 132k miles. It has failed emissions twice. The following are the numbers I am getting.

Emissions Results
Standard HC CO% CO2% RPM
Standard 100 0.50 -- 2500
Test 1 169 0.43 14.4 1702 failed HC
Test 2 136 0.55 14.2 2452 failed HC and CO%

Before Test1, Dealer serviced the car at 120K, changed plugs, etc.
After Test1, I changed the O2 sensor.

Could these show a problem with catalytic converter? Would adding a fuel injection cleaner liker Techron help?

Thanks,
BW

Could be a conditioning issue. Read the following thread and the thread it refers to, and tell me more about the test conditions. If proper conditioning is not enough to get under the limits, the timing modifications will very likely do the trick.

http://www.peachparts.com/shopforum/showthread.php?p=833484#post833484

Duke

I drove about 20 min at 40-50 mph to the emissions facility. Shut off the engine for about 15 minutes. Restarted the car and waited for about 10 minutes. Rev the engine fat 2000 rpm for about 5 min before it was my tunr to be tested. Would these conditions result in these high numbers? Should I have warmed up the cat more?

How do I adjust the timing? I have the Haynes manual and the cd manuals. Are the instructions there? Would changing the spark plugs, air filter, and adding fuel injection cleaner help?

1993 300E 2.8s have the M104 engine. M104's don't have a coil pack instead of a distributor, and timing is controlled electronically. I don't believe timing can be adjusted.

__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

You should not have shut off the engilne!!!!!!!!!!!!!!!


The initial timing cannot be changed. You can slow the rate of timing advance with RPM by removing the R16/1 resistor (do a search on this forum and look at the CD) and replacing it with a "shorting plug" that you can fabricate from a short piece of 10-12 gauge wire and/or disabling the vacuum advance by replacing the short molded rubber tube on the inlet manifold end with a short piece of 1/8" vacuum tubing that you plug with a slug of silicone sealer.

None of the other things you mention will have much, if any, effect unless they are past their normal service intervals.

Duke

Thanks Duke. Today, I passed emissions with great results:

Emissions Results
Standard----HC-----CO%----CO2%---RPM
Standard----100----0.50-------------2500
Test 1------169-----0.43----14.4----1702----failed HC
Test 2------136-----0.55----14.2----2452----failed HC and CO%
Test 3-------21-----0.05----15.3----2466-------PASSED

On the 3rd try, I changed the sparkplugs and added a bottle of Techron to the gas.

Before the 3rd test, I was driving around for about an hour running errands with the AC on. Although I didn't take the car on the highway, I did drive about 40 mph for about 15 miles and I idled the engine at 2500 rpm for about 5 min prior to testing.

Anyone have an idea which of the following contributed the most to my low emissions?

1. Replacing Sparkplugs
2. Techron in the Fuel
3. Warmed up CAT with AC load

In all likelyhood, the catalyst was probably just too cold. Ignition problems will usually cause high HC while CO is low. Your first CO readings indicate that the catalyst was doing virtually nothing. With no catalyst and a functioning lambda system the CO will be about 0.5 percent.

"Conditioning" makes a HUGE difference, particularly on older cars that have some catalyst degradation.

To those of you who have to have periodic emission tests, you must follow some basic rules to ensure that the catalyst is hot at the beginning of the test.

1. Never just take you car to a shop for an emission test, drop it off and pick it up later.

2. Thoroughly warm the car up with at least 20 minutes of driving, preferably including a freeway jaunt.

3. If at all possible, go to a "drive through" place (They are common in California.) They are like a car wash, you just line up behind one of the test bays and wait your turn. Come back if the line is more that two cars deep.

4. Keep the engine at about 1500 revs with the AC or defroster on so the compressor puts some load on the engine.

5. DO NOT SHUT THE ENGINE OFF WHILE YOU ARE WAITING!!!

Duke