Failed Emissions: High HC and CO - PeachParts Mercedes-Benz Forum

Rahulio1989300E · #1 06-14-2010, 05:18 PM

Hello everyone,

I just got back from an emissions test. Had to grab a drink at Sonic afterward, it is hot outside! (1/2 price between 2 and 4PM on drinks)

Bad news: the M103 failed emissions.

Here are the results, please suggest a starting point, I only have 15 days to correct the problem so I can test the car again for free or it is another $40 to test again.

High Speed Results (25mph)
RPM: 1438
HC (ppm): 293 (Standard is 148) FAIL!
CO (%): 7.28 (Standard is 0.94) FAIL!
Nox (ppm): 102 (Standard is 1047) PASS!
Dilution: 17.38 (Standard is >6.0) PASS!

Low Speed Results (15mph)
RPM: 1705
HC (ppm): 284 (Standard is 152) FAIL!
CO (%): 7.35 (Standard is 0.86) FAIL!
Nox (ppm): 98 (Standard is 1146) PASS!
Dilution: 17.55 (Standard is >6.0) PASS!

Overall: FAIL!

lsmalley · #2 06-14-2010, 05:55 PM

Hey you should try seafoaming it. I did it to my 190E after I failed and 10 days later I passed. I can even post pics of the print outs. that stuff is amazing!

david s poole · #3 06-14-2010, 06:00 PM

well your car is running so rich that i'm surprised that there isn't black smoke coming out of the tailpipe when it is running.you prob need to turn the 3mm adjustment at the tower [just behind the plate] about 1/3 to 1/2 turn counterclockwise.

lsmalley · #4 06-14-2010, 06:15 PM

here are the results after seafoam!

JohnM. · #5 06-14-2010, 06:25 PM

To properly adjust the CO mixture you need to hook up a volt meter to pins 2/3 of the round "X11" plug in the engine compartment. The engine needs to be idling, warm, in closed loop (voltage fluctuating). Adjust so that it fluctuates evenly on either side of 6.5v. The aircleaner needs to be on! You will need a long t-handle allen wrench (3mm). You have to press down lightly to engage the adjusting mechanism before you turn the screw. 1/8th of a turn is more than sufficient and give it a little bit for the mixture to settle before making your next adjustment.

If you still fail emissions, check O2 sensor, ignition system. The EHA valve can also fail in such a way that it enriches way too much. You need to check voltage at 2500rpms to ensure the EHA is enriching properly. If your voltage reading at X11 goes off the scale when you revv to 2500rpm, the EHA is the first place to look. You should get at or around 6.5-7V at 2500rpm.

It is also possible the ECU has failed and the car is always in open loop. Your voltage readings at X11 will verify the car if the car is in closed loop or open loop.

Rahulio1989300E · #6 06-16-2010, 10:43 PM

Thank You for your advice. I am in Jacksonville, FL right now helping my sister pack up her apartment for her move.

I get back on Saturday night and will get voltage readings and try to locate the 3mm t-handle wrench.

Rahulio1989300E · #7 06-21-2010, 09:22 PM

So today I finally got around to trying to adjust the mixture. I went ahead, opened the hood, removed the air cleaner and looked for the tower. When I thought I had first found it, I was in denial. Then, I set the air cleaner back into the mounting threads and flashed some light down the hole in it and sure enough it illuminated my problem...
A very big problem.
A very frustrating problem...

Here are the pictures:

Now to give you a brief history...
I have taken over this car from my father since 157,000 miles. Before I took over, he had taken it to 5 different mechanics due to a low speed and idle stalling problem. (It turned out to be the OVP, which I diagnosed and repaired using the information on this forum.) While he threw hundreds and maybe into the one thousand range trying to diagnose the problem using worthless service shops, I fixed it with a $70 part. Maybe I got lucky, but my father is not exactly known for correctly maintaining anything he buys.

I am betting that somewhere along the line, one of those shops did this to the adjustment tower. They probably stripped the adjustment screw and successfully hide the damage by rigging it in this fashion.

I found this online, it looks like a tower repair kit...
I am going to buy this at 10PM CST unless someone chimes in and advises me against it.

The positive side to all of this is that the engine was fine tuned to run mechanically since with the OVP out of commission. A non-functioning OVP leads to 3 systems being offline, one of which includes the fuel computer. One of the cool tidbits that I really like about the M103 is that is it possible to have the engine operate using electronics and mechanical systems or just the mechanical systems should the electronic part of it fail or become inoperative. This leads me to believe that the 300E that I am used to is an improperly running 300E. I am a bit excited to find out what a well tuned 300E feels like.

How my car was able to pass emissions before this is unknown to me. I have done some recent vacuum line work so maybe I have somehow created a vacuum leak that is causing the car to run very rich. Would WD-40 be okay to use to find the leak without destroying the new and old rubber lines?

Once I get the part, what is a good starting point for the tower in terms of screw rotations before I install the part and start the car.

Also, if anyone can send me PDF pages or a link to an online manual for how to get to the tower, please let me know.

Thank You.

Rahulio1989300E · #8 06-21-2010, 09:33 PM

Quote:

Originally Posted by lsmalley

here are the results after seafoam!

That is pretty impressive. I have heard excellent things about Seafoam. I am sure the issue I have is a mixture problem for now, but I will keep this in mind. Thank You.

Rahulio1989300E · #9 06-21-2010, 09:45 PM

Okay, did some Google searching... is this some kind of plug? If so, why is the hole so roughly drilled? I would imagine that MB would do a precision drill for a part this important?

Now I feel like an idiot....

JohnM. · #10 06-21-2010, 10:05 PM

There was a plug there from the factory, and most cars have been adjusted by now. However, that is not a factory plug in the top of yours. And there is not supposed to be a hole in the side of the tower.

See if you can get that plug out. Determine if the adjusting mechanism still works. Patch that hole in the tower with JBweld. If you can't adjust, you will need a new (or good used) air flow meter which comes with the tower. You will just have to transfer your fuel distributor to the new part.

Rahulio1989300E · #11 06-21-2010, 10:13 PM

http://catalog.peachparts.com/ShopByVehicle.epc?q=1989-MERCEDES--BENZ-300e&yearid=1989%40%401989&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6201%3AMBC|1507%3AED|10000013%40%40300E&mode=SS&yearid=1989%40%401989&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6201%3AMBC|1507%3AED|10000013%40%40300E

I forgot to put this link in my post. Instead of tracking down a new tower, could I use this? This is a replacement tower right?

Thank You

Rahulio1989300E · #12 06-22-2010, 09:53 AM

Also,

I just tested the duty cycle this morning.

Here are my results.

With the ignition set to position 2: 69.3%

Reading at first start with cold engine: 49.8%

Reading within 3-4 minutes of start-up started to climb from 49.8% (49.8% --> 54.5% --> 75.8% --> 80.9% --> 84.9%) and eventually settled between a fluctuation of 92.3% and 92.7%.

So from what I understand, the car is properly running in open loop (warm-up) mode. The car also transitions to closed loop (hot engine) mode just fine. but my mixture setting is way off which is why it settles at 92.3%?

Can I rule out a bad EHA and vacuum leaks?

Rahulio1989300E · #13 06-22-2010, 11:18 AM

So I was able to remove the plug in the tower and fit a 3mm hex wrench into the hole. I pushed down and felt the top screw engage the bottom screw and turned the wrench 1/4 CCW to lean out the mixture. This was done with the engine off, and air cleaner off. I removed the hex wrench and made sure the spring loaded screw rose back up to its initial position. I refitted the air cleaner and attached the intake boot and top breather hose. Tried to start the car and it will not. (Starter motor is working great.) I repeated the above procedure except that I turned the screw CW this time. Had to two this twice since the first time got the car to start very roughly and then stall immediately after. Now the car is starting okay again but the duty cycle is still jumping between 92.3 and 92.7%...

Any suggestions?

Rahulio1989300E · #14 06-22-2010, 12:03 PM

Well, I tried turning the screw CCW and CW. Nothing I do seems to change the duty cycle reading. I keep getting 92.3% and 92.7% as my readings. Why is my turning the 3mm adjustment screw not doing anything to the duty cycle? I push the hex wrench down and feel the resistance of the spring loaded screw below it. I feel that something is turning underneath when I turn the hex wrench from above...

What gives???

Rahulio1989300E · #15 06-22-2010, 04:56 PM

I went ahead and removed the Idle Control Valve (ICV) and cleaned it with carb cleaner and tested it with a 9V battery. I had cleaned this part in the summer of 2005 as preventative maintenance, and a lot of brown nasty fluid came out, this time around, not much came out. So I do not thing the ICV is influencing anything.

I am about to test the coolant temperature sensor.