scrwmpwr

Hi everyone, think this fix is posted in another thread but I wanted to make a new thread about it. Ill try not to be too long winded as I tell my story, Ok here goes:

I noticed a thread where a few c55 guys were sharing thoughts on this very issue and suddenly I noticed myself having the same problem. I commented in the thread and said I would post when I have come up with a solution, and I believe I have.

Over the course of a few weeks I noticed my car would occasionally idle rough, usually on cold start, and sometimes the rpms would surge and the car would lurch forward when stopped at a light/stopsign, if my foot was not firmly on the brake.

At first I thought nothing of it until it began to occur more frequently, it turned into a daily event usually on colder mornings/evenings. It got more severe with the motor idling rough, surging and then stalling altogether (once when I was making a left turn through a busy intersection!).

Finally I decided to turn to the forums to see if I was the only one suffering from this dilemma as at first I thought I might have purchased a faulty cps as I had it replaced two and a half months ago. I noticed a few threads about the pros and cons of K&N air filters and believed that this may be the source of my issue - it was not.

In belief that the K&Ns might have damaged my MAF, and that these were the symptoms of such events, I went out and purchased a new mass air flow sensor. When I got around to installing the new MAF I thought it appropriate to remove the K&Ns and reinstall the paper filters as the ones I had were brand new. Success.... wrong, the motor idled a little smoother but the next day the problem had returned

After discussing this issue with a few friends who were techs, I decided to do a little investigating and went back out to the car. This time I removed the MAF and not stopping there I removed the lower piping that routes air after the MAF into the throttle body. Immediately I noticed where the problem stemmed from.

This elbow piece of plastic after the MAF was fouled with crankcase ventilation! (oil). Theres a pcv hose connected to the elbow piece and thats what started this whole ordeal. Not only the elbow piece but the throttle as well, were blackened with carbon. I also noticed the mm or so of clearance around the throttle plate was completely blocked all around restricting air flow.

Identifying this as the reason for my troubles I took a rag and sprayed it lightly with brake cleaner, cleaning both the elbow piece and the throttle body and also making sure to go around the throttle plate. Reversed the uninstallation of the MAF and other components and fired her up. No stalling no surging, just idling as smooth as the day I bought her.

Im pretty confident this is the fix for this particular problem as its been nearly a month and not a single hiccup since. Now its back to

On a side note I did notice that removing the MAF and the elbow piece would have made my CPS install a MILLION times easier than going in from the bottom, for all you DIYers out there. Also a MAF can be had for hundreds less than what the stealer charges. For those who need a new one, just google this part number: 113 09 40 048

Oh and Ive also reinstalled the K&Ns and havent had any problems

Hope this helps, thanks for reading.

SoCalC55

Wow, Deja vu!

This exact situation happened to me last month!

After the first occurrences I had the car towed and it was determined to be my MAF. The dealership replaced the MAF [113-094-00-48] and the car worked fine for a few days.

Then same issues; kept stalling. Hell I even one of the stalls on video.
http://www.youtube.com/watch?v=xTtD37JKHro

Took the car back to the dealership and after a couple days of searching the result was "Clean Throttle Plate, Found Throttle Angle High At Idle, Remove And Clean Throttle Plate"

I was told that there was an excessive amount of carbon buildup which was causing the car's computer think I was traveling at a higher speed then I actually was. It would then tell the engine to take in more air and would stall out the car.

It’s been 2 weeks since the "fix" and cars back to normal, if anything a little nicer throttle response

wawy

Any speculation on what might be causing this (IE: excess idling, driving habits etc)?

AMGnut88

this happens with all cars over time and use, my crapstang used to have it happen all the time, i cant tell you how many times id rip the intake system apart and clean it only to do it maybe a few months later... that being said hard driving made it worse for me personally but then again its a "quality" built American car so.... every situation is different.

SoCalC55

I would guess time and mileage have a factor [I'm at 70k].

I've completed services every 8-10k without a miss, but I have tracked my car and go on the occasional canyon drive. Plus I'm sure the Monday-Friday stop-and-go driving I do doesn’t help the wear and tear on the engine.

kent426

That would be why MB switched to 5w-40 high detergent motor oil. My previous e420 had quite a bit of sludge build up from 0w-40 so I switched and used to oil flush at every oil change to remove it.
I would not use break cleaner around plastic parts, it will eat the plastic over time.

CV8

Hi,

I am from Germany and had the same issue on my car. The local dealer exchanged the MAF, found out that it was not the cause, put the old one back and charged about 750 USD. And their final statement was that I need a new ECU for about 2500 USD.....
Then I found this thread and today I checked my car.
I found the throttlebody to be impacted with carbon. It was cleaned, car runs now much better. Consumption dropped immediately, more torque and sensibility in lower rpm. Excellent!!!

Scrwmpwr, thank you so much for the solution. This was great help and it is much appreciated. This is a great example of how one of the real scopes of the internet is achieved successfully.

Kind regards

ZachG

I also just started to notice the surge/stall when cold. Its only happened twice though, and once warmed up the problem seems to be gone entirely. I'm completely stock (no K&ns etc.) and about 65K miles, all regular maintenance done etc. etc. Have others had success fixing this by cleaning the throttle body?

91RS

This definately happens to almost all cars these days, some worse than others. Stupid K&N oiled air filters will make it dirty very quickly, too. What I thought was very interesting when I installed my supercharger was my throttle body had almost no deposits with 42k on the clock.

radioman

Anybody have any additional solutions for the same problem?


Here's what happened: rough idle (when in D with low RPM around 500). Sometimes idle is fine, sometimes it's so rough it lunges the car and then dips so low the car stalls.

My local mechanic read the CEL code and replaced the MAF. Two days later, same problem.

I read on this forum post that others found a solution by cleaning the throttle body and throttle plate. I cleaned the throttle body and plate (which were dirty), but still same problem. Today, my mechanic reset the ECU and the car ran fine... for about 5 miles. Then the CEL came on and again it's saying the MAF is bad. Any thoughts or recommendations on how we should proceed?!

Your help would be greatly appreciated.

swedepat

Another tip:
When fiddeling with this.
check the hose to the left valvecover that connects to the elbow.
Sometimes it cracks and results in rough idle, sometimes even the checkengine lit up.

Ken311

Have to bring this back from the dead because i think i may have the same problem but I do not have a CEL. When you diagnosed and fixed, did you have one? I've read the codes from the computer and despite the very noticeable roughness there is nothing to indicate there is a problem from the computer

CV8

Hi,

No CEL. Just the surge. And as the previous member said, every vacuum line going or everything flowing air which could be fouled with gas, needs to be cleaned.

gnma

Screwmpwr's post here was the inspiration for me to clean my TB. I Had the same issues. I Cleaned the TB, and the AMG has been running great since then, and we've had a really cold, snowy, icy winter here in NYC this year.

https://mbworld.org/forums/c32-amg-c...ttle-body.html

Ken311, I had no codes either. Best of luck!

gwin

dear god, don't use brake cleaner to clean your TBs.

Take out the MAF, clean it with electrical contact cleaner

Clean your TB with throttle body cleaner

the oil is called crankcase vent oil, happens in all cars, poor designed return line on Merc's part, use a catch can to stop future oil build up.

All cars have a crank case return line, bigger cars/engines just pump more than usual.

amateurs.

91RS

Brake cleaner will not hurt the throttle body any more than throttle body cleaner will. Throttle cleaner is usually stronger. Just spray it on the rag and wipe it clean rather than spraying it directly on the throttle body. And these cars don't have a poor PCV design, there are plenty of cars that get build up way worse than these do. My throttle body had very little at around 40k miles when I cleaned it.

Ken311

Thanks for the feedback. I took the advice here and took a look inside the throttle body. There was indeed a thin band of brownish-black "film" right around the throttle plate. It didn't seem like much but after I spent some time in the garage cleaning this area several times, I am happy to report my issues appear to be resolved.

The surging is no longer present, on/off throttle response is crisp, and idle is smooth as silk once again. I'm surprised at how smooth the car is now, so much so that it feels like the car has NEVER been this smooth since I bought the car. The "film" must accumulate slowly but surely... and as a bonus, my gas mileage is rising from 13mpg with the dirty TB to a much more efficient 18mpg.

I'm VERY glad I stumbled onto this thread

maverik259

This just happened to me this morning. Actually almost caused an accident when it stalled on me in a middle of a turn on my street!

I'll be tackling this after work or this weekend. Thanks!

C230 Mulac

Glad that I bought all 4 breather hoses to replace when I do my valve cover gaskets next weekend, hopefully should be a preventative thing. As advice to all, when it comes time to replace the valve cover gaskets you may as well replace the breather hoses too. They become brittle over time and can break very easily when you try to remove them, especially 9 years old and almost 100k miles like mine.

Good luck mav, let us know what you find out.

Ken311

does anyone have a picture showing where we should be looking?

maverik259

looking for what? the TB, the breather hoses? They're all back behind the engine towards the wiper cowling