Hi
I thought about that I dont no one with this car. No one seems to know
why this is happening and the answer. So this is the next step. If I drove the car daily I would drive it until it stoped but my wife drives it
and you know the story. Any more suggestion are appreciated. Thanks Greg

Well even the older models can develop a surging problem. The only problem is at present I have no ideal. Other than enrichment by the alda is intermittent perhaps. Maybe someone out there has dealt with the surging symptom on 123s.

I have it as well in my 1984 300d but have not really looked for the cause yet. Before you buy the expensive part try posting in the tech session. I suspect at least a few working mercedes technicians keep an eye on that part of the forum... It could even be the transmission..If it cannot decide what gear to stay in. And is rapidly fluxiating.

Replace *ALL* the vacuum hoses and vacuum connectors and vacuum T's under the hood. These are all very inexpensive parts. Probably less than $50 for all of them.

This is my next step. I believe the surging to be vacuum relates. It only happens to me once the engine has warmed up, so I'm thinking it's old hoses that get loose and soft with the heat, and start to leak...

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'98 E300 turbodiesel

Hi Guys
I keep saying surge but more of a lost of power. The strange thing about It happens if you stop the engine 10 sec restart no problems maybe
for 2 days. Is there a sensor in back of the injection pump that sending
information back to the ecm? Thanks Greg

You mentioned in you prior posts that you cleaned the tank. Wondering if you have replaced all the filters? The only time I had this type of problem with my car, was this past winter. Temperatures were down around 25 degrees, and on my last fill up, I did not have the correct amount of anti-gel in my tank that was needed for the amount of fuel I loaded up with. Next morning, got in the car, and started down the road trying to get up to speed. The car had no power, and it was difficult to maintain 50mph. This lasted for about 4-5 miles, and then cleared up without throwing any codes. It is my guess, that the fuel in the lines from the fuel tank to the IP had gelled up due to the cold, and that was causing the fuel starvation, hence the loss of power. I would also check the fuel tank vent to insure that it is not clogged, which may cause a vacuum in the tank as your fuel is used up. Any rubber fittings or lines leading from the tank to the IP should be checked to insure they are not collapsing due to age. I know that is a lot of work, but it is a lot cheaper than putting in a new or used CU and ending up with the same results. Good luck!!

Here is a line that another poster was kind enough to put on the board that may apply to your issues:

96 E300D randomly shutting off

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96 E300d

Greg, I think you and I are having the same problem here, and if so, I don't think it's fuel related. Are these symptoms the same as yours? :

My "surging" is not true surging, it's more like a loss of power. But it's a very rhythmic oscillation of power on-power off-power on-power off every 1/2 second or so. It's pretty sharp and abrupt and causes the whole car to jerk back and forth. Only happens on the highway, never around town.

It also only happens when the engine is fully warmed up. Never happens on a cold engine. Also happens more frequently in hot weather and rarely if ever, in the winter time.

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'98 E300 turbodiesel

Hi Lupin
It sounds like the same thing. Its going on the 3rd day with no
surge. My surge happen around town also. I think there is a sensor
somewhere that controls the injection pump from the ecm but I cant
get any help. All the diesel mech that Ive talked too dont know or tells you to bring it so they can do the same thing that Im doing and charge
you 2500.00 or more. I think its a electrical problem so thats where
I will be looking at maybe together we can find the problem. Does your
car throw a code? My does have this (long story) but If you can, lets
look for some kind of sensor or something thats controling the IJ pump.
Im trying to find out wants in the box connected to the IJ pump or
try to find pictures,diagrams or something. Im going to hold off from
buying the ecm right now until It happens again. thanks for your help
Greg

Greg, I have no codes. I have replaced the following parts within the past year, so apparently none of these parts are related:

1. both vacuum controllers next to the airbox
2. manifold pressure sensor
3. intake air temperature sensor
4. throttle position sensor
5. vacuum change over valve

Replacing some of these got rid of my "check engine electronics" messages and related codes, but the "surging" is still happening... I'm going to do some troubleshooting tomorrow, playing with the vacuum hoses so I'll let you know what I find.....

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'98 E300 turbodiesel

Greg, Here's what I tried today on mine. I disconnected the electrical connector from each of the two vacuum devices (the round ones near the air box) and went for a drive.

I got a "check engine electronics" warning right away, which is expected, but I got *zero* surging / hesitation while driving around like that.

Got back, cleared the codes, plugged the vacuum devices back in, and then drove around and the surging / hesitation came back.

Since both of my vacuum devices are brand new I'm thinking the problem is in the vacuum hoses....

Is this something you can try out on yours, and let us know what happens?

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'98 E300 turbodiesel

Hi Lupin
Went to Las Vegas just getting back (rented a car). Ive taken the
flappers out of the problem by disconnecting them and tieing them open.
The surge hasnt happened for 3 days and didnt do anything. Im going to
open the box connected to the IJ pump and see if I can see anything.
Ill post it if I find anything Thaks Greg

Another test I just did, is to reconnect all the vacuum stuff, but this time unplug the electrical connector to the EGR. I got a CEL of course, but NO surge! Upon closer inspection, the wires to this electrical connector are very frayed, with most of the strands broken. I've just ordered a new connector, so maybe this was the source of my issues? I'll post some pics later.

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'98 E300 turbodiesel

I think this was it!!! Replaced the electrical connector on Friday and now for the past 3 days it has run perfectly with no surging!!!

I'll take a pic of the old connector. Because of the angle that this connector gets plugged in, the wires come out of it and immediately have to make a sharp turn. It's right at this turn where the wires were frayed, corroded, and broken. It is the undersides of the wires that were broken so you have to unplug it to inspect.

The connector is a "3-Pole Female AMP Junior Power Timer Connector Kit" that I had a heck of a time finding where to buy. I ended up buying it from this site.

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'98 E300 turbodiesel

Lupin
My car been running fine for over 2 weeks. My wires are also broken. Ill replace it
also . stay in contact. Thanks Greg

My 97 has the same issues. New GP, flaps and intake cleaned, etc. I have been stumped by this one. I have no codes either. I even swapped the two vacuum transducers that are on the frame around to no avail. I am starting to think it is the IP because it will "stumble" around 2200 to 2800 RPM, which correlates to 50-70ish MPH. I wonder if the 120K miles on the clock have causes an item to wear in the IP because most cars spend a lot of their life operating in this range. If the RPMs are over or under the above, no miss or surge. I can also reproduce this phenomenon manually by turning the TPS by the brake booster, and this miss still happens at the same RPM unloaded. Thoughts?

The surge is gone! Somehow the vacuum transducers on the frame that have identical plugs had the electrical leads swapped. When I examined the miss from under the hood, the intake flap closed as RPM increased. I thought this would be true of the EGR, so I switched them and the surge miss is gone. It appears the miss was actually the engine starving for air.