"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.

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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?

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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

Lucky you.

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#dontdealwithkahlil

A few days later than I planned, but here are the pics. After looking at a bunch of photos of 2.6 engine bays, I'm not sure which way the check valve is supposed to be going because I've seen them both ways, but I'd guess that those reversed have been done so to prevent the valve from opening.





Here are links to the pics in full size too see more detail.

Imgur: The most awesome images on the Internet

Imgur: The most awesome images on the Internet

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#dontdealwithkahlil

One thing about the way the check valves work: they only allow air flow through one way. All check valves connected to lines running to the manifold need to be directed so that the vacuum is flowing towards the manifold. If you pay close attention to the blue/black check valve, there is a small arrow/triangle stamped on it somewhere. It should point towards the manifold.

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1990 190E 3.0L

The black side is the engine side, while many I've seen had them reversed.

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#dontdealwithkahlil

Did the work today. Replaced all the parts lsmalley suggested as well as the injectors and the injector holders and cleaned the ICV. Everything went well other than having a hell of a time backing the EGR tube off the intake manifold and it took almost half hour to get the MAF boot to seat on the TB correctly. When I started the car after the job, it threw code #4-airflow sensor potentiometer for some reason, but I cleared it and it hasn't come back. My idle is smoother and acceleration feels more effortless through the middle of the rev range. Before there was good power on top, but getting her to move while cruising took quite a bit of throttle input. This is what I've read from other people who replaced their worn injectors so I'm glad I went ahead and swapped them while I was in there. I also haven't had the rough start condition that was there, but that seemed to occur at random. Hopefully it's been fixed too.

I tested the EGR and the idle does get rough when opening the valve. That's what the tech was looking for, so I will go back to the smog spot tomorrow and get her passed.

Thanks so much for the help! I really appreciate it.

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#dontdealwithkahlil

So, did it pass?