98 E300 Turbodiesel "hiccuping"
 

I am going to have a hard time describing this, so I wouldn't have any idea how to search previous threads. I re-claimed the MB from my wife in January, after she beat on it for a year. I spent 2K on parts, including a third! front valance and fog lights, front section of the unipanel underneath, second mirror adjustment module, seat position regulator, new floor mats, ect.....(sorry fastlane, I wasn't able to log on at the time I purchased;)) and I had my service brought up to date by my very competent indy.

For the past two weeks, I have noticed that the car seems to be "hiccuping" every few minutes at idle and underway. For a split second, it seems to stutter (and I do mean for only a portion of a second), and the tach needle barely drops when this happens. It runs as strong as ever, isn't smoking and is getting mileage consitent with past performance.

On full disclosure, I had the oil changed last week, but didn't have time to wait for him to do the fuel filter(s) and brought it home to do this week meself. The car has 110K on the clock and new glow plugs.

The stutter, or hiccup is almost imperceptible, but yesterday I drove 200 mi and I noticed it as I usually drive in silence when on certain missions. Could it be a dirty/clogged injector? Dirty fuel filter (I usually replace when I change the oil, but this one doesn't have more than 15K on it)? Air in a fuel line? (all these replaced recently). I haven't put any additives in the fuel in a while and was thinking of running some power service or diesel purge though it to try and help.

Any suggestions appreciated.

might be air getting into the fuel lines. They are notorious for said issue.

Always look for a leak first.

If occurs during decel in low rpm stop and go traffic its normal; is the IP leaning out the fuel mixture.

Ditto what The Don and Terry said. The biggest cuprit with this vehicle is the fuel delivery and filter system. You had already replaced the clear fuel lines.......how about the "O" ring on the little primary filter and the one behind the Shut Off Valve? Any leaking from the six delivery valves on the top of the Injection Pump?....those "O" rings would be due for a change after 10 years if they have not already been done. ;)

I put butcher paper under neath it for a couple of days in the garage and nothing leaked out (yes, running and not).

As to the IP doing its thing--I didn't know that was the case, but the car has never done this before (I have owned it since 27K). Also, it was doing it when I was cruising at 80 yesterday, if that helps.

to the Don--the fuel lines are very new and clear and I have spent quite a bit of time watching them for bubbles and haven't seen any, but is there another way to check this?

Thanks for the responses--I took two years off of trying to deal with this thing myself out of frustration and my wife's abuse of the car, but I am tinkering with an old Army truck right now and am kind of getting the itch to wrench on the benz again. May even get my dipstick pump I made with the advice of this forum out of the basement and start changing my own oil again:D

I always replace the primary filter and its o ring when I change out the fuel filter. I replaced the shut off valve......about a year and a half ago iirc. I let some half ass that owed me money change the oil last year and he took that little o ring off and didn't put it back on the screen filter, and it leaked like a tanker that had hit an iceburg!!

I know the frustration......with the vehicle......with the sub-quality work provided by others.:rolleyes:

FWIW - Like most of us I've had fuel leaks more than once; I've never had one that actually dripped and made a spot on the floor......

From the description it sure sounds like air drawn into the fuel lines, albeit a very mild case. It will hiccup more frequently with more air drawn in. When things get really bad it will require a longer cranking time to start. Is there any smell of diesel fuel under the hood?

- JimY

No smell. Gotcha on the dripping situation. What I have also done is tried to run down all of the fuel lines (that my waaaaaaaaaaay less experienced brain than you guys) I could identify and they all seem to be 'jammed' on the fittings tightly and I haven't noticed any fuel leaking out any where around the injectors either.

It 'feels' like air is in the lines, but as I mentioned before, when I have had that problem, I could always see it as bubbles in the clear lines. If I take it in, I know he will want to replace all the lines again and I think twice in three years is already enough....

Not to hijack my own thread, but have any of you guys replaced steering wheel covers? What do you do, just order one and have an upholstery shop stitch it on? Baby will be near new looking if I get that done!!

On my previous 2000 E430, I installed a new wood leather steering wheel from www.************************. They are a little pricey at $700, but they are original wheels and look and feel like they cost a million bucks.

Performance Products warehouse and showroom is in Van Nuys or North Hollywood, which is pretty close to your buddy's property near the Sunset Strip. Might be worth a trip.

On my old 1993 300E (3.2) "E320", I had my original equipment steering wheel rewrapped in black leather. I forgot how much it cost, but their work was perfect. They were in Pasadena, and are a shop that does a lot of business with GAHH, which makes original seat leather, convertible tops, etc. for Mercedes vehicles of all types and years.

Thanks Sug. I probably won't go the new wheel route, but just want to get it back to stock, as it just looks kind of nasty and since the car is mbtex, the rest of it looks new.

Darnit, I have been searching these posts trying to find someone with the same probelm as mine for such a long time. Tell me if yours does what mine does. Driving at highway speeds, let off the gas, then ever so slightly roll into the throttle and it hiccups. If you roll quickly into throttle, no problem. Now, if you find a straihgt flat road, put the trans in "2" and bring it up and hold at about 2200 RPM, the car surges and surges and surges. That is what mine is doing. I changed all the plastic fuel lines and it apears ever so marginally better, but still there. Mine has been doing it for at least a year now. Can't find a local indy and local MB service apears to know nothing at all about diesels.

As far as the wheel is concerned, pretty straight forward and easy, however, VERY IMPORTANT, disconnect the battery before you unplug the airbag and then make sure the airbag is plugged back in before you put the battery back on or you will get and SRS light on the dash which only dealer can shut off. You will also very more than likely need a good strong air hammer (air powered lug wrench) to remove the 10mm bolt holding the wheel on. Don't even bother trying to kill yourself doing it without one. It will pop right off with the air hammer, but it has to be a pretty powerful one. Did not work with the average one I use to change my tires, had to use a friends that had more a** to it.

Is yours a turbo or a NA 606?

I had a similar hiccuping problem on my 1998 E300D Turbodiesel. In the end it turned out to be a failing bit of the alternator that caused a torque transient load on the engine that eventually broke the belt tensioning feature. That cost me a new alternator and a new serpentine belt tensioner. But it was a weird problem - very much like a hiccup and at times it would do several jerks in a row and then just calmly go about its business. Eventually the alternator stopped keeping the battery charged and a big nasty red warning appeared on the dashboard and that was the way I discovered the problem. Before that I wrote it off as air in the lines that I could not identify a source for, and since it never stopped running or starting, I just kept driving.

Jim

I have the same symptoms at hiway speed with cruise on, I thought for a while it was the cruise cutting out, very very briefly, but later the car was stalling when decelerating to a stop.
I replaced the lines, O rings, DV washers & Orings. Car ran like it did at 50K miles.

BTW, been quite a while since I have hear the phrase Butcher Paper, relatives were real butchers.....I like it.

Good Luck

I'm going to have to go with the alternator explanation because it quit doing that after I had the new $700 alternator replaced. I've put the car out to pasture so to speak at a house that I only use 4-5 times a year because the rentals are kind of pia as the closes airport is 70 mi. away. I had a new alternator, radiator, turbo hose, new AC compressor and new motor mounts installed in the summer at MB of Richmond. $3-4K iirc. The car doesn't hiccup anymore. It was near perfect for a car that age..........until I was up there week before last and noticed the @##$$$#@$$#@damm headliner on the ceiling and sunroof are sagging--I am storing it in my boathouse and I guess it is the humidity because the boathouse is kind of a garage with water access, if that makes sense. Thanks for the info about the steering wheel--but make no mistake--I wasn't intending to do that myself--I'll get the guy doing the headliner to take care of it/

1999 E300TD Hiccup
 

To the first question is the string of replies, mine is a turbo.

I have not thought of the Alternator scenario, but, I can honestly say that this problem was ever so slightly visible about 3 years, 100,000 miles ago. got more noticable about 30,000mi ago. I changed out all the 6 plastic fuel lines about 10,000 ago, and it actually felt a bit worse, but I had a friend helping me that day who, though I always appreciate his help, is by far the most careless person I know, by careless, I mean, not carefull literally. He breaks every tool I lend him etc, but man is he helpful, so I choose my battles (i.e., he has done way more work around my home than what the broken tools cost to replace). Anyhow, I just replaced all the lines again a week ago, and it's definitely better, but certainly still there. I would say about a 50% improvement. For those reasons I kind of doubt it's the alternator as I feel it probably should have failed by now if that were the root of the problem, and it should not have improved by changing the lines "carefully" if it were. I don't see air in the lines while at idle or standing still just above idle, but it also deos not stumble at idle under no load. I was contemplating putting a small reverse camera under the hood aimed at the lines so I can see while I am driving and causing the symptoms, but I am almost convinced that this air I am getting is not coming through these lines because I would imagine that in order to cause a hiccup, the air itself would have to be at the combustion chamber at that very moment in order to cause it. THis hiccup is very predictable, meaning I can make it happen right at the very time I roll into the throttle. So, the air bubble, if there is one, would have to be quickly working it's way to the injectors as I pull my foot off the gas to decelerate and then be right there at the injectors (or one of them) when I slightly roll back into the throttle, causing that momentary hiccup.

There are a couple of black plastic looking things attached to the injector pump which the clip on plastic fuel lines go into. What are there? I understand one is a heater? I also understand that these have "O" rings behind them??? Could these suck air?

Attached to the IP is the shut off valve (black plastic) and the metal lift pump further back. The SOV has an oring between it and the IP; they fail. Lift pumps dont fail often, you can prob ignore it except to check that the lines are well sealed.

The fuel thermostat is in the cyl head and is at the start of the fuel path. Again not a high fil part.

E300TD Hiccup
 

So by the fail do you mean that its the "O" ring that I should consider or the entire SOV? Would it be possible for the SOV itself to be causing the problem? I am trying to make sence of it but I have no idea how they function other than possible some sort of needle valve. I know mine does shut off very well with a notable "klunk", but could there be some sort of "meandering" of that valve that causes it to interfere with flow??? Or, am I just letting my mind run wild and you are simply suggesting I replace the "O" ring behind it (of course it would make sence to try that first). Would a failure of that "O" ring tend to cause air in, or fuel out (I have no leaks what-so-ever).

A bad SOV oring usually leaks. Requires a mirror and light to see up under there. A leaker sometimes causes a delayed shutdown; you turn off key, its in your hand and the engine turns off.

The clunk you hear is prob due to failing motor mounts. Puts stress on the serp belt pivot arm which causes the clunk you hear.

Check the rubber fuel line in the engine compartment where it meets the metal line from the tank... Mine was dried out and leaking air into the fuel flow, it caused hesitation at highway speeds... The Indi who worked on my 98 trimmed the end of the rubber line and clamped it onto the metal line... No more problem...

thanks hobbitts, I will check that rubber hose. Are you aware if that caused visible air bubbles in the clear fule lines?

As far as the clunk, I don't think it's that motor mount again yet. I did change those once. The prvious ones had totally collapsed. New ones made it feel like I traded the car in for an entire new vehicle. I had a interior vibration at idle causes by the steel against steel. THe clunk I mentioned is much more of a "clack" I guess. Best comparison I can make is that it sounds like a rather loud starter solenoid.

I was informed of this issue while having my original plastic lines & o-rings replaced as I thought they were the source of the hesitation... My lines were to old and yellowed to really see thru'... I was told that only one of my o-rings was weaping and not the air source...

After the work was done the hesitation was greatly reduced and totally gone after running thru' a couple of full tanks...

Your fuel line form the tank may well have been bad but, fuel molecules are larger than air so any seal that leaks fuel out can let air in; and some leaks can be small enough to let air in but not fuel out.