300 E smog
 

Ok just took my 91 300E in for smog. Failed the 25 mph emissiin test.80 hc(ppm) allowed. Ran at 100. Need advise.

Slightly high HC can be caused by many factors.

ASSume that the ignition system is in perfect condition?

300E smog
 

Yes it should be. All 20 components checked like catalytic converter PCV EGR Vacuum sensors oxygen sensors says ignition timing is N/A due to computer controlled etc etc. passed without incident. I did a smog background on it and for the past 12 years or so it passed. I bought it at auction as a salvage so i need smog and lamp and brake to get plates. I had head gasket replaced, head resurfaced, tune up done .I filled it with cheveron supreme and drove it home from mechanic. It just runs 20 ppm over on the 25 mph at 1615 rpm test. It did probably sit for a couple years. Do I just need to drive around a bit more to clear out the crap from sitting? I have noticed there is still some sludge residue in the coolant from the head gasket blowing so Im taking out the radiator today and flushing it but I didnt really think that would make it fail.

Any opinions you might have would be greatly appreciated. Thank you.

Slightly high HC is normally caused by very slight misfires.
You could open the spark plug gap to .040" & see if that helps

A better diagnosis could be given if you posted the type of test and complete test results.

California has tagged the M103 engine family as "high emitter profile". The KE fuel system is a factor, but catalyst aging is likely the primary issue.

There are a couple of easy "tweaks" that can significantly reduce emissions that are discussed in the folloing threads:

http://www.peachparts.com/shopforum/tech-help/298724-300te-failed-az-emissions-nox-close.html

http://www.peachparts.com/shopforum/tech-help/123674-passed-smog-barely.html

Emission testing has been extensively discussed, and I've posted a lot of test data and analysis, so you should do some more archive searching.

Duke

post all your smog numbers
 

post the results for the complete test. That will us give a better idea of the problem.

Possibly the catalytic convertor
 

My emmisions were high and I switched the Cat. and all was good. They just visually check the Cat. The smog tech. cant really tell if it is working properly or not. It will just give a bad smog reading like high HC. After My car barely passed I ended up hearing the Cat rattle around soon after. I tuned the car with the bad cat as best as possible then got a new one.
MY readings are now pretty much around 0% CO and 7ppm HC. Before the new Cat. 0.5% CO and 170ppm HC.

You are expecting too much from the emission test, those checks are only to verify the parts are on the car and not a function test.

Did you drain the 2 year old fuel?

A lean condition will cause high HC due to random miss fires that you might not feel.

Clogged injectors ( from old fuel ) will dribble rather than spray, this will cause higher HC.

300E smog
 

thank you all for your help. I tried the spark plug gap and yes it has all new cheveron supreme feul. I drove it for 120 miles still fails. Ive been asked by you to post results. So.. ASM Emission Test Results are:

%CO2 %O2 HC ppm CO% NO ppm
test rpm meas meas max ave meas max ave meas max ave meas
15 1582 14.6 0.0 105 41 101 .69 .05 .04 530 175 55
25 1609 14.6 0.0 80 30 103 .56 .05 .05 487 138 52

15mph passes the 25mph fails.
SORRY THIS THING WILL NOT FORMAT THE PAGE RIGHT. i WRITE IT OUT SO ITS LINED UP BUT WHEN IT POSTS IT DOESNT STAY

300E smog
 

Those are interesting numbers. You have high unburned HC, but low CO, and zero oxygen in the exhuast stream. So the fuel that is burning is burning completely and all the oxygen is being consumed. But you have too much fuel for the available oxygen. You would seem to have a mixture problem - either too much fuel or not enough air. Have you checked the air filter element lately to see if it is dirty or restricted? Cars that have sat tend to have rats nests in such places.

300E smog
 

Ya i had the head gasket changed a tune up put on it. new plugs new air filter. new oil new gas. Could it be the cheveron supreme doing that. I mean its suppose to use supreme gas, so I wasnt really factoring that in. I just dont want to go to a test and repair and them try to tell me its the most expensive thing before I get some opinions. I know the cat is a very real possiblity but I hear they are around 1,000 dollars and you cant put an after mrket so Im hoping to hear its not the cat.

those are about the numbers I had
 

Changed the Cat. and all was good. Does the cat rattle. You could get a Ca emissions Cat. more expensive but also will last longer. It may work better as well. I am not saying for sure it is the Cat but I would bet on it if it were mine.
Actually, I look again and yours are high HC on the 25 mph test and the idle test HC is close to failing as well. My readings were high on the Idle test only.

-Run guaranteed to pass/seafoam bottle through your tank
-Smog your car hot...Really Hot...
-Remove Air filter before smog.

it will help a bit.

To compare

1. When I Failed
Attachment 111604

2. After Doing above (Engine heat was so much that you feel it 3 feet away with Hood open)
Attachment 111605

3. Last year First attempt (Changed plugs, New oil day before smog test, Ran through half bottle of seafoam through intake)
Attachment 111606

Are you sure you cannot get an aftermarket Cat?

This is a CIS KE jet car correct? There should be a procedure somewhere to measure the duty cycle / voltage at the . . thingy on the fuel distributor that alters fuel mixture.

This will give you some sense if the computer is trying to lean out fuel mixture but is at the limit or the computer is forcing things rich.

Has the manual mixture screw been turned at some point in the past? You can get some sense if the mix is too lean by pushing down on the adjuster extension until it engages the real adjuster then pushing a bit farther and seeing if the motor smoothes out. While the adjuster extension is engaged let the adjuster come back up to center, rotate it just enough to grab the real adjuster then pickup, if the motor smoothes out the mix it too rich.

These are very good numbers for a M103 other than HC, and the fact that O2 is 0.0 means the O2 sensor and catalyst are working well.

That leaves excess misfires as the source of the high HC.

What make/model of spark plugs are in the car?

The ignition system is designed for non-resistor plugs (lots of archive discussion on this issue), but they are getting hard to find. Resistor plugs alter the voltage wave form and reduce spark energy at the plug, which can lead to exess misfires - often not enough to notice, but it can show up in the emission test.

RFI resistors are built into the spark plug boots and the distributor cap. The wires should measure about 2K ohms. Pull and twist on them slightly them while testing. It's possible that the plug wires on a lot of M103s have been damaged by pulling the wires off the plugs by hand. I have a special tool that I bought way back when that grabs the metal RFI shield, so no stress is placed on the wire iteself.

There is also a 1 or 2K ohm resistor in the distributor cap towers. My OE cap had a "flaky" tower that would show the proper resistance when holding the cap loosely, but then go to infinity if I put some thumb pressure on the side of the tower, so I replaced the cap.

The combination of resistor plugs and the flaky cap almost caused my car to bust the 100 ppm HC idle limit in the 1995 two-speed no load test. A new cap and going back to proper Bosch non-resistor plugs dropped the idle HC from 100 ppm in '95 to 22 in the '97 two-speed no load test.

Concentrate your effort on testing secondary ignition system components and make sure you have OE equivalent non-resistor plugs installed.

BTW, use periods instead of spaces to line up the data under the proper headings. The software ignores extra spaces but will recognize periods to keep the columns reasonably aligned for easier reading. These are the ASM test results for my '88 190E 2.6 five-speed, done about two weeks ago.

...............CO2....O2............HC...................CO..................NOx
test..rpm..meas..meas..max..ave..meas..max..ave..meas..max..ave..meas

15...1587..15.0...0.0....116...27.....55...0.74..0.09..0.28...791..255...32

25...2638..15.1...0.0.....91...18.....17....0.62..0.07..0.13...730..223...42

Duke

300E smog
 

No Im not 100% sure about after market cat. Just been giving a few opinions from people who have tried and didnt work. Geuss Im just gonna take it to a test and repair and run the diognostic and see what the computer says. Thank you everyone for your input.

300E smog
 

Ok thank you very much for the spark plug info. I did just have the plugs changed when the head gasket was donr and they might not be the right ones. Im gonna pull them and buy one of the recommended make and models in my owners manuel. Thank you