What behavior to expect from a stuck closed EGR?
 

My EGR is stucked closed (the membrane on the actuator is broken) on my 91 300CE (24 V). I isolated the vacuum line that was connected to it to prevent leakage, but I was wondering if I should change the EGR for the moment (thrown so many parts to this car...)?

What to expect from that car running with the EGR stucked closed?

I understand that it should help reducing the Nox if it was working, but any strange behavior to expect from that?

Still troubleshooting an old, old problem here.

I don't think it causes any symptom other than flunking smog tests. But if I am wrong someone will say so...

Yes, since you live in the land of jack-booted smog thugs, you will likely experience symptoms of getting thrown in jail.:eek: Replace right away! They're coming to get you!

Here is my experience:

http://www.peachparts.com/shopforum/showthread.php?t=213239&highlight=glenmore

glenmore
1991 300CE
1990 LS400
2000 C280

Other than somewhat increased emissions, a non-working EGR will increase the engine's tendency to ping under partial load. Before I replaced my faulty unit, I couldn't run anything but preminum in my M103. With a properly functioning EGR, I can now run regular on the hottest days and have absolutely no hint of ping.

DG

All is true, but, the knock sensor will hear the pinging and you will not. It will retard the timing to prevent more pinging, and that lowers HP, and fuel economy.

Mercedes knows this, and thus recommends premium fuel for best HPs and economy.