[jet606]

Hi everyone,

This is the first time I am starting a new topic, so if I posted in the wrong place, wrong way , or didn't find the topic covered elsewhere etc......sorry in advance.

1999 E300, OM606.962, 230,000 kms (144,000 miles), stock condition except EGR delete with resistor as per someone on the internet.

PROBLEM -- occasionally misses at idle (every 5 to 10 seconds, once or twice, just enough to slightly shake the engine), only when warm, only if no load (Park or neutral, A/C off). Car starts runs drives great other than that, lotsa power, no unusual noises, smoke etc, fuel consumption as always (33 to 36 mpg).

The car will only do this when it is completely warm, at no other time (yet...). Any load on the engine (in gear or A/C on), and it stops.

Also, when I step on the accelerator just enough to raise the idle speed a few hundred RPM (normal idle anytime 600RPM), it will accelerate smoothly, may miss when running steady, will definetly miss several times while slowing back down to idle RPM (again, in Park or Neutral, no A/C). -- The car will not do this unless operating warm.

There has been no work done to the car in the last 4 months of driving, and this started about 3 weeks ago.

I did the fuel screen (tank), pre and main filter today, no change, also took all 6 injectors out, had them spray pattern and pop tested -- perfect, no change in behaviour.

List of things that have been done in the past
--injectors cleaned and tested last year
--all clear fuel lines and seals replaced last year (no, I do not have any air bubbles when the car runs -- trust me, I carefully looked)
-- glow plugs last year, when I did those I did look down at the inlet valves and air inlets, I do not apparently have any symptoms of inlet valve seat recession, I also checked again about 4 months ago when I replaced the starter.

My delivery valves are not leaking, the injector pump timing has not changed according to the slip mark from when I had it checked two years ago (required no adjustment).

Could this be a bad delivery valve? Anyone know the symptons or had one go bad? I have read in a few places that a bad copper crush washer could cause this. This is my next step, replace delivery valve seals, copper crush seals and delivery valve springs.

I have also read that a bad MAF sensor can cause all kinds of strange problems....mine does not have a code, or any codes whatsoever at this moment (I suspect if it gets worse the computer with the help of the CPS should be able to give a specific cylinder code....????). I am trying to get my hands on a friends used and defective MAF, his idled smoothly, but he got a code, and no boost.

My next step is to try and isolate the cylinder in a few days, either by loosening one injector line at a time, or, removing intake manifold and very lightly spraying a small amount of ether into one cylinder at a time, see which one stops the problem.

I have done an Italian tuneup, no change there either.

Anyone any ideas???? I am not lost or at the end of the line by a long shot, just wandering if anyone has had this before, and can help out, so I can save myself a bunch of time, which I am always short on....

Cheers and thanks in advance.

 

[Kajtek1]

Looks like in all that work you misses SOV oring replacement. Not likely that gives you a miss, but worth checking.
Diesel question for better exposure might be posted in General section as


WE DO NOT HAVE DIESEL SECTION

 

[jet606]

Thanks for response,

I guess I should have mentioned that I had to replace the shut off valve assembly due to a bad fuel temp sensor about 4 months ago, with new seals.....

Cheers

 

[Olivier A]

After all this I would do the DV. Might not see a leak but they might be leaking.
While at it I do the springs in the DV as well, cheap as chips and may as well replace them

 

[jet606]

Hi everyone,

jet606 responding to my his own problem....as I had clearly stated above, all clear fuel lines and associated seals were replaced last year, and I have no airbubbles in the fuel when the engine runs at idle....absolutly none.....on top of that, ever since I ordered the delivery valve seals, crush washers, springs and tool from the dealer, the car has refused to even miss once at idle. Go figure!!!!!!!

Through a series of uncanny coincidences, with the sun shining onto the clear fuel lines, while leak checking the filter after an oil change, my one hand decided to operate the accelerator potentiometer (to see if I could reproduce the missing idle), gassing the engine a bit, while my eyeball happen to be staring at the clear fuel lines......

Discovery: no airbubbles at steady idle, but as soon as I raised the RPM even a small amount, there suddenly appeared airbubbles in the line from the bottom of the prefilter housing to the fuel shutoff valve. If I raised the RPM even more, the stream of bubbles became larger....then, when I released the accelerator potentiometer, some realy large bubbles made thier way thru the lines, and the engine would miss a few times. As soon as idle was steady, no more bubbles...none at all. The only other place I see bubbles are in the clear line from the base side of the pump going to the main filter (I think this is unused fuel return, based on the flow direction), but these bubbles are much smaller and very few.....because the rest of them are going into the injectors.

Gonna have to fix that one now....go ahead, laugh, I got caught even thow I checked very carefully with a flashlight the first time.

Might be something to remember, check your clear fuel lines for bubbles at greater than idle RPM. More RPM = more suction from the pump (you can actually watch the speed of fuel flow change with changing RPM...courtesy of the bubbles). Lesson learned, no more idle bubble checks.

Cheers

 

[buckstersdad]

I have a similar problem on my 98 E300 w/ 190K. I have all new lines, and new O rings of course on each of them. Replaced O ring on SOV along with O ring on pre-filter. Haven't done fuel tank strainer yet. The rough idle symptoms are frustrating. Just at cold start idle for me. Since I just acquired the car a few months ago I don't know what to expect. The fuel line going from the filter to the IP, the one with the banjo fitting, always has about 2" of air in it when viewing before a cold start. Air accumulates at top next to the pre-filter. Dissipates as soon as you start, but runs rough until warm.

After car is warm everything is perfect as far as performance. I can occasionally see a few small bubbles in the middle line going to the SOV after reving even when warm but they don't seem to affect performance.

Any thoughts would be greatly appreciated.

 

[jet606]

Hey Bucksterdad,

Sounds like same exactly the problem my buddy has on his wife's car. He is supposed to bring it to work this week so that I can observe it.

Seeing a bit of air in the fuel line as you described is apparently "normal", so I have read in other places. Mine also has that, although currently I am beginning to wander, as that appears to be the area where it is sucking air from when running above idle. I gotta make a point of parking car downhill with a full tank and see if there are actually any leaks. I normally park uphill only.

I did have a rough / missing at above idle two years ago, when it was cold outside. Not at idle, but slightly above (1000 to 1500 RPM), only when the engine was cold (start engine, wait untill the glowplugs stop glowing -- 2 minutes, then slowly step on the accelerator and bring the RPM up, hold it steady around 1200, and see what happens). It turned out to be a so-so injector spray pattern. Has them cleaned, one nozzle tip replaced, never came back again.

I will post if I can find anything on my buddies wife's car,

Cheers

 

[RLGDiesel]

Jet606...I am having the exact same symptoms as you are having...slight miss/hiccup at idle only with low load on engine (i.e. park/neutral, ac off, lights off, etc).

I have replaced the fuel filters with prefilter oring. I have also replaced all the plastic fuel lines and the plastic heater near the lines.

Now I was thinking fabric covered return line leak, tank strainer clog, or injector dirt. Plan of attack was removing the plastic IM cover and checking for leaks, replacing tank strainer, and running full strength diesel purge.

It is very interesting to hear your revelation about the air bubbles at higher rpm because I too never looked for bubbles above idle.

Please let me know what you find out. I got nervous because a mechanic friend of mine said he only corrected an issue like this by replacing the injection pump. I would love to know if you can find the exact source of air...awesome diagnosis and post...thanks for sharing!!

 

[jet606]

RLGDiesel,

Do not replace the injector pump under any circumstances unless the car actually becomes undriveable.....too much money involved and possibly wasted. Check www.124zone.com, there are flow checks tests for these injector pumps, I would be doing one of those before anyone can talk me into replacing a pump.

I will post what I find on my buddies wife's car....

Cheers

 

[RLGDiesel]

What's the latest on this?

 

[jet606]

I haven't had much time lately.......My buddy has not managed to bring his wifes car into work, so nothing from that end.

I cleaned all fuel line connection areas with electrical contact cleaner, parked the car downhill in my laneway with an overfull tank of fuel, figuring that if air gets in, then at least a very small amount of dampness shouls appear at the offending fuel line connection. Nothing, zip, zero, zilch, completly 100% dry, every last one of them, I even looked with a small inspection mirror.

I did a few days ago replace the prefilter seals, and the line seals going into the prefilter, no change. Then I very carefully dried with electricall contact area the entire area around the prefilter inlet fitting and housing, and very thouroughly applied silicone all around that area. I will be driving the car later today, and will find out more. It could be that I have a tiny hairline crack somewhere, that will suck air.

Later guys

 

[jet606]

Above procedure of diligently sealing with silicone failed to produce the desired result. Problem unchanged.

Would have spent some time on it this weekend, instead ended up cleaning one very corroded power cable to starter connection where the power cable passes thru the drivers floor. Was intermittently cranking for only a split second, then it would quit. Appears to be fixed now.

Busy all week, try something new next weekend hopefully.

 

[rattling6]

Please keep us posted on what you find. I have the same symptom on my 98 E300TD. Idle is fine until warmed up, then idles rough. If there's any load (A/C on and/or lights on and/or vehicle in gear) it idles smooth as silk. Otherwise at all times everything runs great, plenty of power and apparent boost. Engine and trans mounts are new; air and fuel filter are new; clear fuel lines have no apparent bubbles; MAF has been cleaned.
My gut feeling is that EGR has something to do with this issue. Some day I'll do the control circuit mod to eliminate it. Meantime I will stay tuned here.
Cheers!

 

[jet606]

My EGR is deleted with the electronic resistor mod........

 

[rattling6]

Thanks for the update; sorry if I missed this in your previous posts in this thread.

 

[jet606]

Sorry guys,

My work schedule has not permitted me to spend much time on the car. Since the problem is not getting worse, I have decided to postpone any further work till next year. The car is going for winter storage in another month or so, and my work schedule will not permit me to spend the time I need to.

I did replace a few more suspect fuel line o rings (even though they were only a year old), and seal up the tube connections with silicone, but no positive results yet.

Perhaps someone who drives thier car year round, and has a bit more time than I do will figure it out before I go after it in the spring of 2013.

Cheers and happy motoring

 

[Dieseliak]

I am afraid the mechanic is right - it is the IP

Guys, I registered on the forum only to give you my 2 cents worth of experience, because you have already spent a fair bit of money replacing things that needed no replacing and time that ...probably doesn't count for anything if you love your car. I had the same problem with my 1998 E300TD and after going through the same steps you did I took the car to a shop that specializes in pump rebuilding (in Mississauga, Ontario),they took the pump off, did what they did and $2700.00 later I got my car cured of the "hiccups" and a bag of parts as a souvenir from my costliest car repair ever. If you can live with that occasional miss I'd say just leave it the way it is - the repair is too costly to justify. And it isn't the delivery valves - I had them re-sealed by the same shop months before that due to leak. One more thing - since the original post is by a member from Ontario if you need a shop to check your car try Sharma diesel or Derek's diesel in Barry - these are some of the best you can find in our province (there are some more, but they don't rebuild pumps just know the car very well overall). I have suffered with incompetent mechanics for 3 years to a point that the last one completely destroyed my car so I learned that not even the dealer has knowledgeable mechanics when it comes to MB diesels - I have wasted close to 20 grand in repairs in this car over 3 years and for that kind of money I learned a thing or 2 about them. Nice car when it runs, but really finicky when it comes to repairs.

 

[jet606]

Hi Dieseliak,

Thanks for your thourough response and sharing with all of us. My car is currently parked for the winter, but when I do get it back on the road, it doesn't look like I will do anything more untill it gets much worse.....hopefully never......can't wait for spring!!!

As far as my buddies wifes car goes, he did bring it into work a few weeks ago, but we didn't have the opportunity to let it cool down enough to run rough during a coldstart. I did get the opportunity to run his engine at above idle speed like previously, and I could only see a very small amount of airbubbles (like a really small amount), while performing previously described engine acceleration from under the hood. Needless to say, his engine idles down perfectly.

Now if I could only find a cutaway drawing and figure out how a pump that is only being supplied with fuel can create air.......

All the best,

Cheers

 

[EDBSO]

I believe fuel flows 1 to 6.
1 2 1nd 3 are sucking the rest are pressured.

fuelflow.JPG (image)


Just curious, does the manifold have to be completely removed along with the hard lines to remove the injectors?

 

[Kajtek1]

Injectors are on the top of the engine. all you have to do is loosen the steel lanes and disconnect leak hoses to get them out.
Nice drawing EDBSO. Very clear and is right.
To make it more clear from 5 the fuel goes via SOV and enters injection pump by the fitting on back of the valve not shown here.
6, 7, 8 are leak lanes.