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Old 08-13-2008, 06:06 AM   #11
itasca2008
 
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Default Re: Engine miss on light acceleration

Jon

Now it gets interesting (and confusing). What your SM 2007 says doesn't make any sense to me.

In my V6 engine, part of the exhaust gases flow from the back of the engine through the little cooler on the passenger side to the underside of the EGR valve. The butterfly is also on the underside. And that is where all the soot accumulates. If the valve is not closed, then the exhaust gases can move upwards and they exit the valve through the little metal tube and they go down into the connection from the intercooler to the intake manifold.

My valve is closed when not energized. The ECM opens it with a PWM signal, and that's where the trouble starts. The opening force is an electrical one, which works against the closing force of the spring of the valve. If another mechanical force - sticky axle or sticky butterfly - joins the process, then the position of the valve is not where it is supposed to be, may be only for a short time, but here we might feel the miss.

The SM 2007 says the valve is open when not energized, and that the ECM will close it. And they say that the valve is in the connection from the intercooler to the intake manifold, throttling the intake air. Sorry, but as I described above, my engine is different (or more likely, the manual is wrong).

The SM 2006 makes sense to me, and I have no reason for any doubts.

About the pulling of the EGR valve: I'm only pulling it out, so I can clean the underside. If you want to replace it, or remove it from the vehicle, then the procedure in the SM is the correct one.

Anyway thank you very much for your last post. This is how we learn the most.

Marcel
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Old 08-13-2008, 09:22 PM   #12
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Default Re: Engine miss on light acceleration

Thank you all for your responses.
I'm gonna pay more attention to when it does it, though the comment about highway travel at a fixed speed followed by a change of throttle position makes the most sense. VERY hard to duplicate, so the service dept. will have a time fixing it.
As far as me working on it, that's why i bought a new one, so i won't have to. Spent a lot of years fixing cars, to the detriment of my back health, and swore i'd never do it again. Fortunately, we can afford new. Just hope the dealer can find and fix it.

Jef
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Old 08-13-2008, 10:41 PM   #13
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Default Re: Engine miss on light acceleration

Much of the 2007 Service Manual makes little sense to me, as well. However, it is a resource and a foundation for discussion and the beginings of practical experience. Sprinter-Source and posters' practical experiences have more weight in my mind.

Thanks again, Marcel.

Jef, good luck, man. Please post about your dealings with the dealership.

-Jon
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Old 08-14-2008, 09:22 PM   #14
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Default Re: Engine miss on light acceleration

Quote:
Originally Posted by cedarsanctum View Post
Hi All,


During the trip i experienced what seems like an engine miss after slowing down and then applying light throttle acceleration. At times it was a rather loud, hard clunk, other times just a small bit of surging. Feels like either the engine cutting out, or the transmission thinking it needs to shift and aborts it in mid-shift, slamming back into gear. Or it could be a stuck valve (EGR?) opening suddenly. It also seems to be affected by elevation, the higher up, the more severe the 'miss'.


I have not taken it to the dealer, yet, it's hard to make it do it in town. No trouble codes show up anywhere in the system, though i don't have a scanner. It never went into limp mode, just a miss or 2 and back to business.

Any ideas? Anyone else experience this?



Thanks,
Jef
I have just had exactly this problem with a 2007 3ltr V6 cdi, albeit in a 639 Vito, but the same motor.

http://www2.mercedes-benz.co.uk/cont...l_Edition.html

As you say, no visible codes. I can check fault codes via the diagnostic port but still none show. It would not miss behave to order so dealer, whilst helpful, could find nothing wrong. Happily the egr valve finally failed completely putting on the engine managment light and causing the motor to go into 'limp' mode ie. reduced power and only max 3000 rpm available. Dealer found fault code, diagnosed failed egr, replaced egr and now running perfectly again.
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Old 08-15-2008, 12:33 AM   #15
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Default Re: Engine miss on light acceleration

That Vito is a screamer. 204 bhp out of the same engine that's limited to 154 bhp in the US Sprinter. Of course the Sprinter engine in the EU is limited to 184 bhp. Max hp target (set by software in the ECM) must be a function of available fuel quality and relative time spent at full output. Lower weight and smaller vehicles have lower power demands so the engine spends relatively less time at full output. Don't have the data in front of me now, but I believe the M class cdi in the US puts out 220 bhp. Of course, it's likely very seldom at full output. And, most owners probably don't expect 100k+ mile service. Injector hold down life is undoubtedly related to peak cylinder pressure magnitude and number of such cycles experienced (higher pressure means fewer cycles to failure and lower pressure means more cycles to failure - probably an exponential relationship). Failure comes by metal creep and maybe even fracture brought on by metal fatigue.
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Old 08-15-2008, 02:33 AM   #16
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Default Re: Engine miss on light acceleration

Hi Leaky

Thank you very much for your post. It is the missing link between this thread and the thread "Lost power suddenly"!

Could you please answer the following questions:

1) At how many miles did you feel the first miss? (Mine was at about 5,000 miles.)

2) At how many miles did you go into LHM the first time? (I did not up to 10,000 miles, and then I preventively cleaned the EGR valve. Between 5,000 and 10,000 miles I experienced about 20 misses.)

3) Could you please post what is written on your new EGR valve? ( Mine says: Wahler, 109315, 00005320C5, AC5071002673. Just wondering, if a new version is out and if they changed anything.)

Your answers would be helpful and much appreciated. Thank you.

Marcel
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Old 08-15-2008, 07:31 AM   #17
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Default Re: Engine miss on light acceleration

Quote:
Originally Posted by itasca2008 View Post
Hi Leaky

1) At how many miles did you feel the first miss? (Mine was at about 5,000 miles.)

2) At how many miles did you go into LHM the first time? (I did not up to 10,000 miles, and then I preventively cleaned the EGR valve. Between 5,000 and 10,000 miles I experienced about 20 misses.)

Marcel
Thank you Leaky, great info, and if you have the sport-X version, you have a very nice ride!

And thank you Marcel, great questions.
So far most of my 'misses' happened on this trip, about 5-7 times, i think. The odo just turned 3000 miles halfway through this trip.
I did experience some kind of miss a couple times when pulling away from rest stops before this trip, all low speed in 1st gear. Felt more mechanical than engine. General consensus on that was it's normal, part of the drive-train.

It's hot in town this weekend, so i might take a drive and test out some of these theories. I'd really rather not experience LHM on a long trip away from home, like the southern end of Baja or something.

Jef
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Old 08-15-2008, 11:24 PM   #18
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Default Re: Engine miss on light acceleration

Marcel[/QUOTE]
Quote:
Originally Posted by itasca2008 View Post

1) At how many miles did you feel the first miss? (Mine was at about 5,000 miles.)

2) At how many miles did you go into LHM the first time? (I did not up to 10,000 miles, and then I preventively cleaned the EGR valve. Between 5,000 and 10,000 miles I experienced about 20 misses.)

3) Could you please post what is written on your new EGR valve? ( Mine says: Wahler, 109315, 00005320C5, AC5071002673. Just wondering, if a new version is out and if they changed anything.)

Your answers would be helpful and much appreciated. Thank you.

Marcel
1) The miss/hesitation first manifested itself at approx 12000 miles although after the replacement egr, I realised that there had been a slow deterioration in the low end power (1200 - 2000 rpm) for much longer than that.

2) LHM did not occur until the egr actually failed (I think that the actuator motor failed) and lit up the engine managment light at approx 20000 miles.

3) Wahler 109315, 00005320C5, AC5081852728 and from the side of the actuator motor SONCEBOZ 2.4 /3

If you do get caught out by the LHM activating, I found that by unplugging the air flow meter (big plug) on the rear of the air filter box, full revs are available again although still at reduced power. I think that I read it on this forum somewhere, and it worked for me.

My miss appeared to occur at approx 1400 rpm and approx 17/1800 rpm and seemed to happen more after being in traffic.

The problem with the egr valve itself seems not to be so much the rotary action (although I am sure that it can stiffen up over time) but the up and down movement on the shaft which although also spring loaded, seems to stick and hold the valve blades away from the valve body allowing exhaust to pass through the valve all the time. This was certainly the case when I cleaned and checked mine.

The 204 bhp tunes easily to 250 bhp, just don't ask how I know.
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Old 08-16-2008, 12:05 AM   #19
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Default Re: Engine miss on light acceleration

Hi Leaky

Thank you very much for this additional info. I'll keep everything stored in my brain and I'll see, how I'll be doing in the future. What I learned is, that there are at least some indications before the vehicle finally goes into limp mode. So for now I have to figure out, how well the cleaning process actually helps. If we have to buy a new EGR valve every 20,000 miles after the warranty expires, ... but maybe they are going to improve the design.

Marcel
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Old 08-16-2008, 01:30 AM   #20
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Default Re: Engine miss on light acceleration

I found that cleaning the egr did help a lot. I used PTFE spray to flood the valve spindle bearing (not the actuator motor) from above and worked the shaft up and down against its spring to free it off completely as mine would stick slightly off its the seat. It seems to be just a poor design.

Just remembered, we had a software update about 6 months ago to address 'surging' at low speeds which I suspect was related to the egr problem.

It makes you wonder how many other owners are just accepting the low speed problems as a characteristic of the vehicle, possibly advised as such by the dealers who seem to have little knowledge of this problem and even less interest. 'It's only a van' appears to be the attitude in the UK. I am one of the lucky ones as I do understand how things work and have one of the very few good Mercedes commercial dealers local to me.

Look here, you are not alone.

http://www.mbclub.co.uk/forums/showthread.php?t=42037

The 3ltr cdi is not that common in the UK, most Sprinters are ordered with the 2.1 ltr 4 cylinder motor.

See here

http://www2.mercedes-benz.co.uk/cont...Panel_Van.html
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