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.

__________________
From 300CE to SLK230K

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

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

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

__________________
Prost!

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.

__________________
1990 300CE. Garage kept all its life. Looks & Runs Like New. Everything works. White w/Palomino int. Pioneer 12 CD player in the boot. 17" Enkei LX-F Chrome wheels w/Falken Azenis ST-115 225-45 tires. Tinted windows. Black sports grill w/Euro clear front lamps.