My friend has a 1990 300SE (M103)with 172K. Runs perfect, but the car has a funny issue that my 300SEL actually has from time to time.

*When going steady, say at 40 mph, on steady acceleration the cars engine power will fluctuate, as if she is working the pedal. Even on moderate acceleration it will do it. I have driven it and felt it and actually mine will SOMETIMES do this. Not at any certain speed, but pretty much at any speed hers will do this on steady acceleration. its like it gets too much gas, then too little, too much, too little, etc.

She said hers has been getting worse over the past few weeks. It also has a slight splutter at idle, so I am guessing it may be related?

Does anyone have any ideas what this is and whats the fix? I was once told it was possibly the airflow sensor potentiometer, then someone said plugs, then someone said something about there is something under the air cleaner on the back of the throttle body that needs adjusting?

Not sure about her car, but I know that mine will always start very easily, hot or cold... however I do have a CEL that will come on 15 seconds after its first started then on for only about 45 seconds after that. Not sure if its related or not. Have not had the code read, as I dont know if a local auto parts store can check this car like they can others... where is the hookup for the computer on these cars?

Any help appreciated.

start with a systematic basic check is the best way.
for starters replace the fuel filter may be clogged and accumulator if very old .
mak
300se

My 300E does this a little bit too at random, but not enough for me to care....and it doesn't have any running issues and idles fine. I'm guessing potentiometer or EHA on mine as well. Someday I will look into it. I'm taking the "don't touch what is not broken" approach for now.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
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'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Thanks. Where are the fuel filters on these cars? Wheres the accumulator?

Thanks. Well, I think what has her concerned is that it did start out to be minor, its seemed to have gotten worse pretty quickly (over the course of two weeks) and I think she is concerned the car will eventually stall out or something. I kinda have those concerns with mine, but its only minor at this time and dont happen all of the time.

Perhaps I will at least recommend a fuel filter change, as it seems easy and cheap.... probably change mine as well, because I have no idea when it was last changed.

I just replaced the fuel accumulator (filter too) on my 560SEL, and this problem persists.

On my 300SE, I have replaced the fuel pump and filter, and it has this issue sometimes too.

On both cars, it appears to be most noticeable on medium acceleration, being much less apparent on grandma or lead-foot driving.

I think it has something to do with feedback or something. It just has the feel that the computer is continually adjusting something that interferes with steady fuel flow. I am guessing it's the EHA valve, but not the valve itself, rather what controls it. The thing does control chamber pressure, and that seems like the most obvious spot in the fuel system for a surging like this to manifest.

The car has a new TPS as well, which was my first guess.

Maybe its the FPR, I dunno.

__________________
-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

Oh, and if she is developing a sputter at idle, that points to a vacuum leak, assuming everything else is well maintained. My 300SE was the same way. Eventually the sputter will turn into an intermittent stall, and once the weather warms up, it'll really become a pain.

__________________
-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

Thanks for all of that info.... since my 300SEL is kinda doing this its an interest to me as well. I also have the occasional sputter at idle and sometimes the idle will jump up when stopped in gear, etc, but its all unpredictable on my car... some days its fine and on my car, temperature dont seem to make any difference.

Its good to know that the fuel filter didnt make any difference, because I was going to change this on mine, but I dont see any need if its not going to help. My car gets excellent MPG, it gets 20-21 in town... pretty good I think.

You mention the EHA valve and at one time I thought mine was leaking, as I could smell gas a little under the hood, but never seen any gas leaks. SO STRANGE, but this started when I switched to non-ethanol gas.... it persisted for about two months, but I was told it was not a big deal... then the store where I bought gas stopped selling non-ethanol and whats so strange is that the gas smell went away and has never returned and thats been about 6 months ago... not even a whiff of gas from under the hood. I am not sure if it was just a coincidence though or not.

I am sure the uneven acceleration (surges) is not a major problem, but is kindof annoying to me. I was going to have it checked, but my car is for sale anyway and I will probably let the new owner address it and come down on the price a little.

Thanks again