E320 cdi V6 Rough Running when warming up

[MACHBUFFET]

Hi Guys
2006 E320 cdi V6 Sport 90k FMBSH

I'm having an issue with my E320 cdi and wondered if anyone could help.
Some time ago I posted on this forum about the tapping noise that was coming from the engine. Following several visits to indies and MB dealer, I was told that it was quite normal and they all do it to some extent. However, recently I happened to visit another indie and they said straight away that it was an injector seal. He replaced all six, reground, new bolts etc and the car sounds totally different - soooooooo quiet and no tapping.
However, it's left me with another headache. Since picking up, from start to warm up, at around 1000 to 1600 rpm there is a misfire. This happens whilst stationary and when driving. If you try to hold revs within that range it misfires. As the car warms up, the range narrows to the point that at about 70 deg coolant temp (gauge reading) it does it at 1000 rpm and eventually disappears altogether when revving in neutral, but still slightly noticeable under load while driving (noticeable in slow moving traffic).
Doesn't affect the acceleration, it pulls like a train and once warmed up, is hardly noticable.
I suspected a fuelling issue, as the exhaust fumes are particularly pungent during this period. As a precaution, I went around all of the injectors and noted the numbers on the tops. I compared this to the smooth running printout he gave me and found that no1 and 2 were swapped. I went back and he re programmed them (took three attempts mind) and seems to be correctly numbered now but its still doing the same thing.
At all times, cold and hot, the idle quality is excellent. This only happens when you bring it off idle.
Recently I have also replaced the back pressure sensor, and had a compression check done (all excellent)
I'm not an expert, but thanks to these forums I can at least try to figure out some ideas. Would it be a temp sensor issue? I've heard they don't always throw fault codes.
What about crank sensor? Do they signal the load + engine speed to ECU to meter fuel?
Also, re the numbers on the injectors and programming them into the ECU. How does the ECU know the correction values for each injector ever made from this number. Does it require some sort of live internet connection during input to download the specific value for the injector. It's just a jumble of letters and numbers, often having no numerical content and I just wondered how the ECU can determine values from this. I was told that each injector has it's own value and must be correctly programmed but wondered how the values are obtained by the ECU.
The other thing is, I'm just assuming that the cylinders are numbered (looking from the front) Drivers side - 1, 2, 3 front to back and passenger side - 4, 5, 6 front to back. Is this correct?

I've booked back in to see them next week but in the meantime, I was wondering if anyone could help. I love the car but it's driving me mad and causing a bit of concern.
Thanks in advance
Barry

 

[MACHBUFFET]

Anyone?

 

[MACHBUFFET]

Wow!
I guess it off to Mercedes-Benz Owners' Forums for me then!

 

[SL300-24]

Yeah Television should be able to sent you the papers.....

 

[camerafodder]

You've asked a number of technical questions on a site you haven't contributed to since May 2012. Perhaps you should display a little more patience? It is after all a free site and you addressing what amounts to a bunch of friendly volunteers, not a 'paid for' service.

 

[Bakili]

Would you rather have right advice or some like me have no clue reply with stupid reply with wrong diagnoses.

Be patient my friend someone with knowledge will answer your question.

 

[SavMan]

Based on the fact it has happened since the injector / seals have been changed and swapped around, I would guess either

A) One or more of the injectors have been incorrect coded to the ECU
B) One or more of the injectors is faulty


The best thing is to get live data in STAR and replicate the exact issue you should be able to see what cylinder/s is/are causing you the issue.

 

[MACHBUFFET]

Quick update from today. Phoned the Indy and asked if I could drop the car off, let it cool down all day and test it in he evening from cold. He had conducted a smooth running test at idle and all was well, but I asked him to conduct it above 1000rpm, cold.
He phoned me later today to say that smooth running at idle was fine but as soon as he reached 1150rpm no5 injector shot up to +5.7 and of course the others tried to compensate. Revs up to 1500 rpm in 100 steps and no5 never went below +5.07.
We've ordered a new injector and will be fitting next week. I'll post back with an update when it's done.
Also had this feedback from
E320 cdi V6 Rough Running when warming up - Mercedes-Benz Owners' Forums

And it quotes

"Star is not accessing internet when coding. I think injectors has pre manufacturing sets, which are known in advance and are not changed during model generation. For example CDI2 model injector has only few sets. What I don't know, how the set it determined, is the injector tested and codes defined according the test results, or is there 'model variations' inside the model series which determines the coding.

ECU has additional electrical adaptive corretion value for each injector, which tries to balance differences between the cylinders. WIS says injector should be replaced if value is more than +- 5, but troubles can be already if value is around 3.

Now you have pezo injectors I assume? They are known to fail. When solenoid actuated injector failes, it shut down the engine. When piezo fails, it 'shut down' itself for while, then it recovers and start working again if nothing drastic. That sounds like your case."

Seems to point to what the problem might be, but hopefully I'll have more news next week.

 

[MACHBUFFET]

Hi guys
I've picked up the car after the injector replacement injector was fitted. The injector was original MB stock and has been correctly programmed into the ECU.
The car runs much better now but still not perfect. Originally, the misfire was there under all conditions at 1100 rpm to 1300 rpm, almost disappearing when fully warmed up. Now it is much improved, with only a slight misfire detectable at 1100 rpm whilst driving. This happens only during a temperature band from about 50 deg to 80 deg when warming up. We notice it as we pull out of our road and into slow moving traffic, going up a slight incline and engine at about 1100 to 1200 rpm. Wife can't notice it at all but I pick up a slight misfire under these conditions. It doesn't last very long and once the car warms up, it's gone and it drives A1. The Indy is on hols for a fortnight now, so I'm going to go back at a later date and try to replicate the misfire whilst hooked up to STAR.
I've learned a few things though. Namely that originally the car did several smooth running tests and the injector readings were perfect. It was only when I pressed the guys in the workshop to let me replicate the exact issue that suddenly no. 5 injector went up to +5.07. Took my foot off the gas, let it back to idle and best behaviour again. Lesson for me is that just because a car passes a smooth running test at idle, doesn't mean it will off idle. From feedback on the forum, the type of injector used in the V6 cdi can misbehave and intermittently sometimes before packing up. In some cases they just go on for years doing that and although the spec is +5 for replacement, according to advice from a kind forum member they can begin to present problems at +3. If you're having any problems like this, talk to your mechanic and offer to be present when they run the checks so you can show them exactly what it is you're experiencing. Preferably whie it's hooked up to STAR, as in my case once warmed up it all but dissappeared. The Indy confessed to not having seen an injector behave like this before and had I not pressed the matter, was going to start travelling down the road of replacement turbo, inlet port motor and possibly looking at the EGR valve. It might have been a very expensive journey to ultimately end up where we started.
I'll keep you posted and report back later when I have news.
Thanks to you all for your help and advice.