jimbo1mcm

This is info from another website that could be useful:
"I have a 2005 CDI just 1 year old, 21K miles on it. I've had similar issues. After about 6 months the car would accasionally cough and stall, or cough then run.......coasting off a highway ramp, asked for power, got none. Acceleration was limited and engine noise was distinctly louder...... MB found that stopping and restarting it restored power. They told me this was the computer putting the car in the Limp Home Mode. This code occurs when the computer thinks that continued use might damage the engine, so it restricts output to half throttle and transmission to lower gears.

AFTER THE EGR VALVE WAS REPLACED, CAR IS BACK TO DELIGHTFUL SELF....."

It looks like they are having some EGR problems. I am putting a note in my Operating Manual regarding the loss of power problem.

kort677

seems to be a common problem, this happened to me and it was the same problem

saffrontiger

holy smokes, that sounds exactly what i've been experiencing with the sputtering and hesitation. Sorry for the basic question but what exactly is an EGR valve?

saffrontiger

Kort have you had any issues after this? Did the CEL come on? Did they also take a look at the transmission. Just trying cover all of the possible diagnoses. Ontop of the diesel smell and leaks which have now been fixed, the ongoing hesitation continues especially after driving at highway speeds and taking my footy off the gas pedal (ie. exiting the ramp) the car begins to hesitate and feels as though if i don't give it some throttle it will stall. Frustrating but after all of this, i still love the CDI. Go figure
Jay

kort677

Nothing came on, the car just went into limp mode, took it to the dealer and they replaced the egr valve, no problems since then and that was 30k miles ago

CE750

Exhaust gas recirculation valve.... does exactly what it says, and keeps the engine warmer inside, and aids combustion.

BudC

It actually feeds some exhaust gas back into the intake manifold to reduce ignition temperatures and that will reduce NOX.

The valve should only open at part throttle. At idle or with a closed throttle, the valve should close to prevent exhaust gasses from getting to the intake. If the valve fails to close you can have a rough idle or similar problems. With modern engines, electronics and sensors are used rather than the old vacuum method so there could be something else besides the EGR Valve at fault.

EGR is designed for one purpose, to reduce emissions. Otherwise, it woudn't be there.

MBblackCDI

I wanted to thank all who contribute to this forum, I have learned alot, and saved countless $$ from the info on these forums. My '06 CDI has been misbehaving, and finally pinned it down to the EGR. The P0404 code led me to the EGR, I took the EGR apart, and cleaned the soot under the plastic cam cover, still goes into limp mode. Aftrer removing the EGR again I was able to determine that the tempered steel return spring was broken and the cam would not return to the home position. If you follow other threads, there's no way to rebuild these due to the welded cam. A little patience and a lot of research yielded the following: Mercedes offers a rebuilt Wahler EGR also if you buy one from the dealer, there is a core charge. You can pick one up for under $400 delivered, then return the core. I hope this helps someone , as this forum has inspired and helped me.......

clvincent

Great info, thanks for posting this

MBblackCDI

I will update when I recieve the parts, I expect final cost to be around $370, From an online parts site, after shipping back the core. I haven't seen anything cheaper.
With the $$ I save I will replace the flexible disc on the driveshaft, then onto the upgrading the calipers and rotors......

boogsenior

The turbo has an actuator in it that sticks because of carbon in the vanes. If you take the air filter off start the engine and run it at about 2000 rpm spray water in the intake about half a bottle of distilled water in a spray bottle , take your time and shoot the water in slowly. This should free up the vanes in the vnt turbo. Once the carbon is freed up in the turbo it will all go out the exhaust. Worked for me after getting all the BS from the dealer. I actually used my windshield washer reservoir and routed the hose into the plenum after the Maf sensor. While I drove I squirted water from the washer button into the engine. Not a sniff of limp home mode now for over a month. I drive it every day and lots of miles.------now working for over two years. cost me 5 dollars to fix

MBblackCDI

Well finally i got the credit for the core on my EGR from parts.com, so far no issues with limp mode or CEL. In my case I know the EGR was the issue, I still get a little black smoke every now and then, I think something else is amiss, but I am happy with it. after shipping and returns, the EGR was around $375, was the best deal I could get. I took photos, will post when I find camera......
Anybody know where I can get a decent tune for low $$ I'd like to go with GDE but I have kids to put through college.

Al Spaeth

Help please- My 2006 E320CDI goes into engine limp mode occasionally. No warning lights no visible problems. Only happens if the car is not driven for a couple of days. After a short drive, shut off and restart runs fine.
Took it into my dealer who confirmed there are no problems only the electric motor that operates the limp mode is faulty.
Quote for parts and labour $3K.
Is there any way to override limp mode via the computer or eliminate limp mode mechanically?
Car is like new, 150K km full dealer service history from new,
Thanks

ot1

A limp mode electric motor??? Konigstiger where are you? Is there such a servo?

konigstiger

Common limp mode causes:
- Faulty mass air sensor (MAS)
- Electronic throttle actuator problems
- Broke, cracked, loose wiring harnesses
- Faulty brake light sensor
- Corroded computer module contacts (i.e.: transmission control unit, transmission shift module)
- Problems with transmission valve body and/or conductor plate

Ask dealer to clarify exactly what it is they are suggesting to replace.

Doug Ferguson

I'm fairly new to CDI, but have been a tech for a long time now retired. Bought this car (2005 E320 CDI) with 160K miles. . Kept going into limp mode. Some times no check engine light or code (using very basic scanner). Finally got it to throw a code for EGR. Took the valve off. Noticed the valve return spring wasn't able to close the valve reliably. The valve stem was carboned up and sticking. Used chem tool to saturate down into the stem guide and stroked the valve open and closed for quite a bit until I was able to dissolve the carbon. Used Kroil to lube the guide roller and stem. The action of the valve is now night and day better. Closes nicely. Put it back on and voila! The electrical part of these valves is bulletproof as far as I can tell. The only failure that might spell real trouble is if the return spring is broken. You would have to grind the weld off the shaft to get the arm off the shaft and figure out a replacement spring, then tack it back on. It seems barring anything breaking, the failure mode is these valves just sticking, and a good cleaning and lubing will fix em right up.

shakerv

My 2005 CDI with 200k miles has the coughing problem and occsional loss of power. Check engine light came on and it threw the EGR value issue. After changing the EGR valve, the check engine light went away but the problem of coughing hesitation and occasiional loss power still exists although diminished. I looked at this blog and someone had posted switching to lower gear and blasting the carbon deposits in entry ramps to highways and stop driving like an old lady. When I switch to the lower gear, the power is back on. Any suggestions from the group is much appreciated. There are not too many trained mechanics that I know of who can deal with Mercedez Diesel who are reasonable in Sandiego area. Thanks in advance for your input.