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Discussion Starter #1
Well guys, with the new year comes another emissions inspection. I especially dread this process, especially since it took me 8 months the last time and I ended up with a waiver. Time served doesn't count which means the 8 months ate into my next 2 years. I have decided to post again after reading a thread started by Bosanci28 dated 9/28/08, who seems to have had similar problems (Bonsanci28, hope you resolved your problems). I am providing my history in the attached files with hopes of getting advice from some of the experts on this forum. Since the initial testing in 2007 I have changed plugs, wires, cat, resonator, o2 sensor, cleaned and replaced egr, and have tried all suggestions/solutions in beteen. The results you can see in my readings from April 2008 (Sorry, no graphs for this reading). Now as an aside, I had my oil changed yesterday and while waiting decided to talk to the head mechanic about my emissions readings. I showed him the the graphs and the first thing he says it that its running rich. He also indicated that what i see in my exhaust is the result of excess fuel being dumped in the line and not necessarily oil burning. You can actually smell the odor in the exhaust. He says he has seen this problem on these cars before and its the result of a fuel modulator (could be regulator but can't remember). Basically something that controls the flow of fuel has gone haywire. I asked about leaky injectors and other things and he says no. He says the part in question is about $250 and $100 to repair(thoughts on what this might be?) . Not sure what to do at this point, but would surely appreciate advice from our experts. Would like to get this problem resolved before August inspections. Not sure what to believe at this point since I have had varying opinions.
 

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You got two choices when it comes to fuel pressure damping/modulation:
1. The fuel pressure regulator in the engine bay near the fuel distributor
2. The fuel modulator in the back where the fuel pump and filter are.

Another suggestion is to check your EHA valve for proper operation. You need to check the fuel differential between the upper and lower chambers of the fuel distributor and adjust the EHA screw for proper pressure. Next you adjust the air/fuel idle mixture next to the intake.
I would highly suggest that you do all this while testing the exhaust. So have your mechanic stick a probe in the back while those adjustments are being made.
 

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Discussion Starter #3
When I took it to an indy earlier this year, they said it was running rich. Supposedly they made the adjustment. But at the same time they said stay away from stop and go traffic. I would do better at high speeds.
 

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Discussion Starter #4
This guy indicated that he worked on benzes for 7 years. If I decide to let him take a look at it, what questions should I ask?
 

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One thing to do is pull your spark plugs and see if they are wet/fouled. If so, that cylinder probably has a leaky fuel injector. Same thing happened to me recently and caused high emissions readings. Pulled plugs, found the fouled one, cleaned it up, replaced the injector and passed the test. If all plugs check out good, then you need to move onto figuring out what else is causing it to run so rich.

Has this guy worked on MB in general or is he familiar with the 126 series and CIS-E fuel injection in particular?
 

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Discussion Starter #6
i will start the process by checking the plugs to see which ones are fouled. A few questions. 1) Since I haven't driven the car in a couple of days, is it necessary to restart for a few minutes to get the fluids going or will the cylinder be wet with fuel? 2) I assume fouled plugs should be dark and crusty, maybe? 3) If i need to replace the injector is this a difficult procedure? If not, what are the steps and what specific tools will I need. I remember replacing an injector in a car years ago, but don't quite remember the procedure.

Not sure what Benzo's this guy worked on. All he said was a certified mercedes mechanic for 7 years. He was quite busy so I didn't get a chance to have a detailed discussion.
 

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Yup...def. looks to be rich.

Fuel pressure reg is entirely possible.. A set of fuel pressure gauges and a fellow that knows how to read them would tell you if the pressure reg is out or not..

EHA could also be out of whack..

Was it an OE O2 sensor or a mustang sensor?

This is where wide band O2 sensors and stand alone A/F meters Really come in handy..

Jonathan
 

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Discussion Starter #10
Jono,
It was an OE sensor. Although the CAT was replaced, sometimes I wonder if they installed the O2 I gave them. One thing though, the check engine light has never come on.
 

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I've found a lack of CEL means nothing these days.. I've had cars come in who's mixture was astoundingly off w/o throwing a CEL.

Jonathan
 

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Discussion Starter #12
Thing is, I took it to a reputable Benz indy several months ago. They said it was too rich. Something about 50% out. They supposedly made the adjustment, but seems like it is still out of whack. Maybe I need to check the EHA for leakage and check for fouled plugs. Although the EHA appears to be an easy repair, adjustments would be needed and I wouldn't want to muff things up. Also, replacing EHA may not be the answer in which case throwing money at wrong solution.
 

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Again, getting a wide band o2 and A/F meter would answer SO many questions and allow you to tune the car Right.

I've seen more then one O2 give good lamda/duty cycle reading @ idle only to be a Mess while cruising/WOT etc..

Jonathan
 

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Discussion Starter #14 (Edited)
Seems like this wide band O2 and A/F meter might be an expensive piece of eqipment for a shade tree guy. What's the cost, would it be worth getting, and where would one get this piece of equipment? And, if a shade tree decided to do this, what are the steps to use and what to look for? A lot of questions I know, but seems like good info to have what ever my decision on how to proceed.

BTW and FWIW, a visual check of the EHA showed no signs of outward leakage.
 

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Any dyno shop/tuning shop will have one one hand..they are about 2-300$.


Purchase tool, drill hole in exhaust, weld on bung, plug in wide band sensor, do some Minor calibrating (takes about a minute) and off you go!

Jonathan
 

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Discussion Starter #16
Well, I pulled all six plugs tonight to assess their condition. The plugs I have are HR 9DC R6 588. All plugs appear to have a modest buildup of what appears to be carbon. These plugs have less than 1k miles on them. Would appreciate opinions/thoughs based on the discussion in this thread. Pics 582(right t o left) are the front 3 plugs from front to back. Pics 584(right to left) are the rear 3 from front to back.
 

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Those plugs look pretty good to me..


I am SOOOOOO glad that I don't have to worry about these kinds of tests here in upstate ny. The only ones we have are for OBD II (1996+) vehicles.
 

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Plugs are wrong for one... Other then that they look to be OK.

Get some NGk BP6ES's.

What were they torqued too? They look mighty grubby around the base..

It would be better if the pics showed close up/macro of the actual electrode from the side..high res would be Good as well:)

Jonathan
 

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Discussion Starter #19
Stuff around the base was anti sieze that was on my hand. Did not have torque wrench so tightened with ratchet until snug. What is proper torque value? Camera would not get in focus close up but electrodes were good. Carbon buildup around metal base which I thought was indicative of excess fuel in cylinder not being burned. Thoughts?
 

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Discussion Starter #20
Plugs were what was recommended as OE. I guess not. Will need replacements if you have. Stuff around base is too much anti sieze. Un able to get macro close ups with camera but electodes were in good shape. Metal plates @ base had carbon build up which I assume was excess un burned fuel. Thoughts? No torque wrench just wratchet and snug tight. What's correct torque value?
 
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