OK,,, I give up
 

Taking the 320 in to my indy tomorrow to try to get the idle surge figured out. Through the help of the forum, I have tried everything imaginable, but it is actually getting worse, so it's time to bite the bullet. Will let you know what comes of this diagnosis.

Okay, Pete. Good luck! Just don't get upset . . .







I'm sorry. I know I shouldn't have said that. I just couldn't help myself.

After owning these Benzes since 1993,,,, I don't get upset any more.:D

Don't feel bad...my idle surge was the first thing I ever posted here (2001) and I never solved it either. My indie discovered the bad vacuum hose just last year.

If it is a bad hose, I'm going to have it gold plated and hang it on my wall.

Check the EGR pipes for blockage.

http://www.continentalimports.com/ser_ic20134.html

Did the new EGR about 2 months ago. Surging started shortly after that and am wondering if there might be a tie in there.

I remember one of Johnhef's friends trying to diagnose a problem like this. He was a very seasoned MB Master Technician and an excellent diagnostician. He said problems like this were a real bear to diagnose correctly.

Having said that, I guess anybody would have a tough time doing it. This is probably why mechanics are often accused of "throwing parts" at problems. That doesn't make it any easier when you're the one BUYING the parts, though.

I have seen EGR SOV valves not closing completely ..this will effect egr closing.
The test is to put a BB in the vac line between the egr element port and the SOV and run the car for a few days.
No surge = you have narrowed down the cause.

I also do a manual egr test and part of that test is to make sure the egr SNAPS shut.

As the problem came with EGR change, it also possible that you have a simple vac leak anywhere in between the egr and the intake at the engine ..this could be as simple as the mount bolts/gasket at the intake side or a loose fitting of the cross tube from the valve..

The idle surge problem with my C280 was caused by the purge valve/regeneration valve. Every time the code was tripped for it, I would clean it out with some WD40, as per Arthur's method. I finally got tired of doing that all the time and I just bought a new valve Instant cure. Your E320 has the same M104 engine so it might be worth looking at. To test the purge valve just hold it in your hand while the car is running. You should feel it pulsing, like a heartbeat. If it isn't pulsing, it ain't working. It takes all of 3 minutes to replace, no tools required.

I was just out checking on the car and they told me "it's fixed". Said I had 2 bad vaccum hoses under the car some where. I hope to get more specifics when I pick the car up. Great news though.

I want to see a photo of these two bad vacuum hoses gold plated and mounted on your wall. :D

Son of a gun Paul,,,, they threw them away already.:D

Oh for the love of God.... :wacky:

Crank vent tubes, is what they said they replaced. Under the intake I see 2 new rubber like tubes that are about 1 inch in diameter. Whatever, it sure cured the problem, I think I can stand a dime on its edge on the hood with the engine idleing.:D