I have a 1997 E300D that runs great most of the time, my problem is that when your driving on the highway or anywhere you are at a certain speed (55-60mph) for a while the car begins to surge.(Not extremely bad, but bad enough you can feel it) When you accelerate the car or let of the gas the surging goes away. If you start at a redlight and hammer the car it runs perfect no matter how fast you go until you plane out and start running a constant speed then it begins to surge. I have changed the fuel filter and the pre-filter w/ oring. I have also changed the egr and taken the intake off to look for broken vaccumm lines and such. This hasn't fixed anything. I have added fuel system cleaner also. The car did have a code in it that said something to the nature of Fuel Temp. Sensor Malfunction. I erased it and it hasnt' returned but could that be the issue? Any suggestions would be great. Thanks

if you haven't done this already, you might want to check the resonator flaps in the crossover pipe for freedom of movement or broken vacuum actuators. If the flaps are stuck, or an actuator broken, it will not produce a code, but performance can suffer. The speed that you mention is just about the speed that the first set of flaps start to open.....just a guess on my part..good luck.

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96 E300d

There is a small vacuum hose on the top of the intake on driver's side that comes from small nipple on manifold and goes to a pressure sensor. Mine cracked and fell off and was causing what you describe. Where are you located?? Can you get the RPMs up above 5000? The flaps were my first problem, I took the cross-over and resonance intake off and cleaned well. Becareful though the wires are brittle..

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Dennis
2006 E320 CDI Black/Black Leather. Nav, HTD Seats HK stereo 32000 miles.
2000 VW Passat 1.8t 300,000 miles as of Dec 09, 2009 original owner
1997 E300d Silver 300,000 miles As of Jan 05, 2010
3rd owner SOLD

Also, you could swap electro switches controling vacuum signals to the EGR and res flaps to see if the problem moves from one set of flaps to the other.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Hmm, I think I have the same problem. I described it in my Bosio feedback thread, but I didn't mention that in addition to the highway pinging I also sometimes have surging at the same time. I'm starting to suspect the flaps. As I said my EGR flap doesn't move anymore. The other flaps are harder to check for proper operation since you can't see them but I did lube them recently.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

The flaps can be badly crudded up from exhaust gases due to the EGR. After I disabled my EGR valve, I removed the manifold and crossover pipe (to replace a glow plug) and was amazed at how dirty it was. No wonder the PO had to have the dealer replace a resonance flap at least once over the years!

I have another glow plug to replace (#3 just failed) as soon as the new one arrives and expect to find a much cleaner set of pipes when I get inside.

Jeremy

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"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