Hey guys, I've got an '09 ML320 Bluetec with ~137k miles on it. Yes, you read that right. Anyway...

Under acceleration, the car bucks big time when the engine is warm. Seems as though there is a loss of power or some sort. Brought the car to the dealer and the service adviser said that the engine has carbon buildup and a bad catalytic converter. The tech then recommended I replace the intake manifold.. yeah right.

Would carbon buildup cause this sort of "bucking" issue?

With regards to the Cat, is there a tune available for bluetec engines that allows a gain of engine power and a way to disable the O2 sensors? I plan to keep this car another 3 years until 300k miles so I'm not worried about the Cat, just passing emissions. An increase in HP and gas mileage would be nice too.

Thanks,
Charles

 

Intake gets clogged from combination of EGR gases and Oil Vapors from PCV system. Its probably a stuck intake flap. Find a good indy who will pull the intake and have it dipped to clean. If you belong to MBCA then maybe there are some indys in CT that other members will recommend

 

Thanks for the response! I have an indy that should be able to check it out. The carbon buildup causing the flap to get stuck makes perfect sense.

Is there a filter that I should change as well in order for this problem to not arise in the future? Also, perhaps you know, is there a good tune for these motors?

Charles

 

There is no fix other than a good run on the highway to blow out the carbon. A form of this plagues all diesels. Its just a function of the EGR sysstem and PCV workig to create a bunch of crud in the intake. On late 90's MB diesels came up with a way to plug off the EGR without throwing any emissions codes. Not sure it can be done on the newer versions. If you browse around the W210 forums and search for clogged intake there are pics of what it can look like. I had the stuck flaps on my 1997 W210, I think thats becuase the previous owner did a lot of low speed drdiving with short trips. Basically you have the PCV system dumping oil vapors in to coat the the intake, and then hot EGR gases combining to solidify those vapors into crud.

Congrats on the mileage BTW. Great to see later models with higher mileage. In March I sold my pristine 06 E320 CDI with 99000 miles to a guy in Central Ct. So if you see a black E320 with mudlaps in fantastic condition its probably him.

 

Interesting. Most of the car's mileage comes from the highway (obviously). Do you think doing a few WOT runs would help to maybe open up the flap? The dealer recommended I try a cleaning solution which we run in the oil and I believe gas tank. I'm going to have my independent shop do it this week.

 

Looks like you need an Italian Tune Up.

In other words drive it like you have stolen it for a day or so !!

 

I would be hesitant to add anything to either the oil or fuel. Addititives might have a negative impact on diesel particulate filter. It might be that the "puck" part of the pcv system may have to be replaced, its kind of an oil separator. Also you might find www.alldatadiy.com interesting to look over, its a cheap subscription and contains alot of information about servicing, TSBs, recalls etc.

 

So, had the car serviced on Friday. Oil change, fuel filter, air filter, and cabin filter change. Also tried the additives into the fuel and oil. Cleared the check engine light, however it came back on after about 40 miles of driving. The car still hesitates occasionally but I haven't experienced the major bucking going uphill that there was before. This may arise though as I do longer trips, I've only driven ~5 miles at a time so far.

I think the next step is to pull the intake manifold and have it cleaned. The code is for the EGR something or other, so I believe the flap in the manifold must be getting stuck.

 

If its an EGR code, you might be lucky that its just the EGR valve/flap thats sticking. See below, there are a lot of devices that are part of the EGR system.Also, there was a TSB about a small EGR tube, that if plugged can cause sluggisness and limp home mode.


Exhaust gas recirculation (EGR) is active at low load and speed ranges. Exhaust gas recirculation is carried out according to engine load and engine speed. To do this, the CDI control unit (N3/9) reads information from the following components:

• Left hot film mass air flow sensor (B2/6) (except model 461)
• Right hot film mass air flow sensor (B2/7) (except model 461)
• Hot film mass air flow sensor (B2/5) (model 461)
• Charge pressure sensor (B5/1)
• Charge air temperature sensor (B17/8)
• TWC [KAT] temperature sensor (B19)
• Pressure sensor downstream of air filter (B28/5) (except model 463)
• Pressure sensor downstream of air filter, right cylinder bank (B28/5) (Model 463)
• Accelerator pedal sensor (B37)
• Crankshaft Hall sensor (B70)

 

In the first post you mention cat converter and chipping to ignore the 02 sensors, what exactly are your codes? Please clarify
There are exhaust gas temp sensors in the exhaust, cleaning them can certainly help clear fault codes and it takes 5-10 minutes to do so, they are very easily to remove and shoot with maf cleaner or brake cleaner. The DPF can be cleaned also, it is common for them to clog up and a "replace at XXX miles" in your owners manual, but you can pressure wash them out and reuse for longer.
I have not played with the egr or intake on a v6 diesel yet, it looks very time consuming to remove and clean and very delicate (lots of wiring connectors to deal with, not the part itself but the job). It is possible it needs cleaning, but start with the egr valve itself and the flap motor in the intake. Dealers always quote new parts they never fix anything anymore, just replace. Run lots of fuel conditioner in your tank, powerservice or howes or whatever is local but not alcohol based ones, it will help a small amount by keeping the exhaust cleaner and less particles to recirculate through the egr. Research which is the best diesel in your area, tdiclub.com usually has a chart with upto date info on who's fuel is good, your looking for 50 cetane is possible. Change your oil more often then the 10k miles interval, the less vapours the cleaner it will stay and make sure your using low saps oil (mb 229.51) These are all things that will help see 300k miles.
You can find lots of useful info on the sprinter forums where owners actually drive their cdis and some even diy.
As for reflashing for performance or emmissions I have not found a source in north america yet...looking too. If you want better mpg and power remove the DPF and find a source to keep the check engine light out (emmissions system changes reflashing), it will net quite a bit mpg by breathing better. This will also stop the regeneration that runs rich and heats up the dpf, it costs alot of fuel to do this.