kept throwing the P0120 code which has been linked to the EGR as well as TPS based on this forum's knowledge base. I found the vaccuum lines to the modulator that controls the flapper were stetched out an old and most likely leaking so replaced those. Also replaced a cracked vacuum line that goes from the exhaust manifold to the TPR electrical unit. The car will drive longer now without throwing the code but will eventually do so after htiing hwy speeds for 10-20 minutes. Any ideas of what might eb causing this? I also notice the flapper butterfly valve does nto move when I rev the engine while in park, should it??? Any help much appreciated.

by the way

The flaps may be all crudded up with soot from the EGR valve mixed with oil from the turbo. Time to take the intake apart and thoroughly clean it. To keep the problem from recurring, defeat the EGR valve.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

previous owner recently did that job along with 'fixing' to the egr so don't think that is it. I am planning to remove the intake crossover to have a look though, just in case, but she is breathing easy due to the egr 'fix' so I don't think this is the issue. Think the modulator that controls the flap may not be operating properly, any way to test this??

Does the flap move when the engine is idling and you give a little additional throttle? You should be able to see the external parts move. If they don't move at all, then the flap actuator may not be getting any vacuum.

Depending on the thoroughness of your first check, you may want to look again for damaged vacuum lines. A vacuum line not directly connected to the flaps could be leaking and leaving insufficient vacuum to operate the flaps properly. If you found some bad lines, there may be others.

Go back to the solenoid valve and see if it works. You should be able to unplug its electrical connector and apply 12 volts directly to its terminals for a second. You should hear a click and, if you disconnect the vacuum hoses, should be able to attach a separate hose and blow through the valve. If the electrical part of the solenoid is working, you should be able to turn it on and off with 12 volts and blowing through it confirms that it is actually working.

If the flap works when you test it, then it may not be getting the correct signals from the computer, I forget what Mercedes calls it, that operates the flaps and EGR stuff. Check for broken wires, loose connections, etc. The computer is usually reliable and besides is very expensive, you don't want to think about having to replace it.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

thanks, I will do the needful and report back once I get a spare minute between work, law school and the 10 week old.

OK, I adjusted the butterfly valve that controls the flapper right near the EGR, so that adjustment bar is as short as possible and shortened the vacuum tube to the modulator, which I made too long upon replacement. Also, replaced the line from manifold to TPS sensor. Took off crossover pipe to inspect and clean, at least considering its a diesel and these things are known for being clogged with untold sludge, and vacuum line to flapper on corssover pipe looked good. Wife drove 80 plus hwy miles today and no CEL. sweet, other than my onw time time about a $1 worth of vacuum tube.