What are the symptoms of a bad EGR valve? EGR tube is clean.....

I just resealed the front timing cover again, changed injector seals, changed IAT sensor, plug wires, checked every vacuum line in the engine bay.......i cannot figure out why my engine has a rich smell to it.......my new O2 sensor lasted 2 months, and i am getting a code for o2 again......

when providing vacuum to the valve (by mouth ), i could not hear anything moving or clicking.

There is nothing else i can change in this car, seriously...I just don't like the exhaust smell...I even smell it when opening the door which makes me think something is leaking in the exhaust/ egr system.....

thanks

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1993 300E, 2.8 M104 .....

You need a vacuum pump, your mouth wont do anything, but for the gas smell I would look into the cat and the carbon/charcoal canister.

What is the carbon/ charcoal canister and what is its job exactly?

Thanks,

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1993 300E, 2.8 M104 .....

I think the canister absorbs fuel vapour ??

As for the vaccuum. I beg to differ about sucking the vaccuum line. I did this in the past to test the EGR on my E320. When i sucked on the vaccuum line on the EGR, the car stumbled and ran rough. WHen released, it ran fine.

The canister is indeed part of the evaporative emissions system, designed to absorb stray fuel vapors and recycle them through the intake manifold. Agree with Kiwi that one can test the EGR in that manner.

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

So you test it with the car running? no health hazard involved with this ?

any how, if stuck open, will it cause mixture issues? if stuck closed, what is the side effect?

thanks,

Edit: Mr. Learner, where is this canister located on the m104?

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1993 300E, 2.8 M104 .....

EGR stuck open will cause obvious idle quality problems, and car may not even run at all at closed throttle if bad enough. Doesn't take much vacuum to open a normally operating EGR valve.

EGR stuck closed (or EGR tube/passages blocked) usually doesn't cause any drivability symptoms at all, possibly some spark knock under load, but WILL cause an emission test failure for high NOx. The emission test failure is about the only indication for most of us that the EGR is staying closed (at least on pre-OBDII cars) since it doesn't noticeably affect engine performance when closed.

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Erich Loepke
2010 Ford Focus
Currently Benz-less

So I grabbed the vacuum line going to the switch over valve, and hooked it directly to the EGR hose. car stumbled immediately after that... i guess it is working? ......

So ideally, it should open for a few seconds upon warming up? and then close at normal temp?

thanks

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1993 300E, 2.8 M104 .....

Sounds like it is working.

I *think* it should remain closed until operating temp. Then only open while cruising.

I have seen people swap the air pump and EGR vaccuum hoses at the switch over valve. This can cause rough idle when cold.

To check the correct orientation. Take both vaccuum hoses off the of the switch over valve. Start the car cold. The one with vaccuum on it goes to the air pump, the other goes to the EGR.