The only way to know for sure if the cat. is at fault, is to take readings before & after it.
Maybe you could pay someone a couple of bucks to do this for you.

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2007 C 230 Sport.

I suggest just replacing the cat. I had similar problems with another car and messed around with the EGR and the engine controls for months to no avial. Installed a new Cat and poof the exhaust was clean as a whistle.

David Roseman
Long Beach, Ca

what about going to junk yard cutting one off and running two cats ?

Replacing the Cat makes sense. I had a truck that failed. I replaced the cat at the suggestion of an experienced mechanic and it passed with flying colors. Afterwards, I realized that the EGR was completely disabled, but it passed OK anyway.

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83 W123 240D
76 300D, "Lil Yellow Car"
1978 Cessna 172N 180 HP Mod

"If life ain't fun, I'm not interested"

The important things are those that you learn after you know it all.
Chip Foose

Build a better mousetrap and you will REALLY infuriate corporate america.

I know it's an old thread, but tagging on here and hopefully someone can help. I've also got an issue with smogging a 2.6. Mine's a '92.

The numbers are good for my smog, but it failed due to an EGR issue. Basically, it's not passing gas. The tech took a vac pump to the solenoid and the diaphragm moved, so I don't think that's the problem.

Here's where I am with my troubleshooting (all done idling):

I pulled some hoses to see if I can tell where the holdup is. There is no vacuum at the solenoid, but there is vacuum at the relay just after it. I swapped the electrical connectors to the identical relay that is just next to it, and there was no change. I'm not sure if these should be open during idle, so I'm not sure if this should have changed anything.

Please advise as to what I should be checking next.

Thanks.

Sent from my HTC One_M8 using Tapatalk

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Watch him go!!! link

#dontdealwithkahlil

Because the diaphragm moved doesn't mean that its holding a vacuum. I would just replace the EGR. You said your numbers were good, so I'm assuming you passed as far as emissions, but you failed because the operation of your EGR. So replace it and problem solved.

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1990 190E 3.0L

"The numbers are good for my smog, but it failed due to an EGR issue. Basically, it's not passing gas. The tech took a vac pump to the solenoid and the diaphragm moved, so I don't think that's the problem."

...same question, if it passed the NOx cutpoints and the EGR valve passed the functional check, what's the problem?

Duke

The EGR holds vacuum. The problem is that it's not actually recirculating the exhaust gas back to the intake side. After searching it seems like it's probably that the EGR tube is clogged with carbon. I'm looking to clean it, but can't access the nut on the intake. Has anyone done this job?

Super easy. Remove the air cleaner housing, remove the fuel distributor, and the nut and tube are right there. I haven't cleaned the tube out before, but I've accessed it multiple times. Actually had access to it last night while resealing throttle body. PM if you have questions.

Attached Thumbnails

 

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1990 190E 3.0L

Excellent! Much thanks! I will update with the results.

Cold start valve nut: 12mm
6 fuel injector nuts: 14mm
Main fuel line: 19mm or 17mm
Fuel return line: 19mm or 17mm
3 nuts holding fuel distributor: 10mm
Only need to disconnect one hose on right of IACV.

I suggest replacing IACV hoses while you are there, also might need the nylon fitting going to the air meter boot and replace gasket on throttle body. You can also use black silicone rtv. 4 pea-sized drops on each side and use a gloved finger to spread it and cover the area in a thin coat. 5mm hex to remove 4 bolts on throttle body and 5mm hex to remove 2 bolts on cold start valve. Also consider replacing boot on bottom of fuel distributor. It's about 11 various nuts and bolts all 10mm that need to be removed.

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1990 190E 3.0L

Thanks for the suggestions. I will definitely take note and address those things next time the air cleaner is off (probably very soon).

Here's what happened:

I noticed the check valve on the vacuum line was backwards and flipped it. Then to test the EGR tube for blockage, I flipped the EGR so it wouldn't be in the way, started the car and checked for vacuum on the tube. It was sucking pretty good, so I thought I had it all figured out.

I went back to the smog check and the tech put the vacuum pump on the EGR while the car was running, but the idle didn't fluctuate meaning the gas still wasn't circulating to the intake. Next thing to do is clean out the EGR. I had a good mind to do it while it was off the car, but since I had two eureka moments I thought I was all good. If anyone has any ideas please run them by. I need to pickup another vacuum pump (last one was a AutoZone plastic cheapo that died) so I can test and not waste my time driving back down there.

Post a picture of your engine bay.

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1990 190E 3.0L

Sure thing. Will have to be tomo when the sun's out. Mainly the exhaust mani side and all the EGR parts or anything else in particular you want to see?

__________________
Watch him go!!! link

#dontdealwithkahlil

Just the exhaust side. I don't have a check valve on my egr lines....but it doesn't really matter because I'm smog exempt now ��

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1990 190E 3.0L