The title explains my issue fairly well. 2005 E55, 94k miles.

Just performed the 100k mile service, new plugs/wires,air filter, oil, trans flush etc.

On cold starts I get some vibration and what feels/sounds like misfires from the motor. The car surges and hesitates occasionally on acceleration, deceleration and in between shifts. The vibration continues in Park or Drive, at stoplights, etc. for 15-20 minutes. After the car is warm, the idle is perfect and the car drives great. No CELs.

My indy mechanic believes the problem can be fixed with a new fuel filter/pump (the one on the top of the tank, not the one in between the fuel banks that would require a whole new tank).

Question for you guys with the 55k motors is, have you experienced this type of an issue? Was the problem a faulty/clogged fuel filter/pump? Was it something else like an EGRV? An idle control valve?

Any input would be appreciated. Thanks

-Ken

 

it might be the secondary air injection pump (SAI). You can diagnose it by temporarily turning off SAI and seeing if it fixes it.

https://mbworld.org/forums/w211-amg/...rough-sds.html

 

If I had the equipment to do that I would. Is there another way to check this unit? Would the secondary air pump cause a rough idle when cold only? That is my differentiating factor between many of the other cases I found through the search. I have no idle problems when warm unlike most folks who have posted here.

 

Anyone?

 

Check your primary 02 sensors, as at 94K they could have weak output.

 

Check the throttle body plate for sludge buildup on the backside as well as around the diameter, known to cause idle issues.

 

I thought about this but wouldn't failing sensors throw CELs?

Will do thanks

 

When was the last time the fuel filter was changed?

It's required service around 60K miles.... expensive, yes but important. A lot of guys seem to miss this service item either because they think it's too expensive (~$600) or they just never realized it was supposed to get swapped out.

Clogged filter = low fuel pressure & flow. At WOT, you could end up starving the motor for fuel... and that's when the REALLY expensive problems happen.

I don't know if there is a way to read fuel pressure through the OBDII port or not, that would a convenient way to do a quick "sanity check" on the condition of your fuel filter/pump....



-G

 

Good to know, I believe this is what my mechanic was getting at. I'm sure it has not been replaced. Will look into it and see if the diagnostics can confirm.

Thanks,
Ken

 

check plug wires and plugs..

 

they were replaced a little more than a week ago

 

Make sure that all of the wires "click" sound when put back onto the plug. Some do not and can cause the issue you are having.

 

Im having the same issue but its not every morning. Hmmm

 

Mine did this as well, ha several bad plug wires, did all the plugs wires and the PCV chamber reseal on the valve cover today, and it is smooth as can be now

 

Had the fuel pump/filter assembly replaced last week, and while it does feel smoother when driving warm, the idle when cold still shakes the car and sounds like it is misfiring. Still experiencing surging/jerking/hesitation between shifts, etc. when driving while car is warming up. No CELs as before.

I'm going to have to start checking more possible problem areas. Taking a look at the throttle body/actuator plate this week as well as the secondary air pump. Could it be a vaccum leak?

I have written off any issues with plug wires because it would be causing rough idle/operation all the time...same with O2 sensors (had these go bad on my C32 and they throw CELs). It's very confusing that the car can run so smooth when warm but so rough when warming up.

 

Thoroughly cleaned the throttle body yesterday and that seemed to be part of the problem. Now the surging/hesitation/jerking is gone.

However, on cold starts the idle is still very rough. After 5 minutes, it goes away and the car is smooth as silk. This is making me lean to the secondary air system, but I am just beyond confused as to why a malfunction in this system would not be throwing a CEL or at least some error codes while the rough idle is occurring...

Input...suggestions?

 

Did you do ecu adaptation after cleaning the Tb (default initialization)?

 

I have not yet (usually do that at the gas station), I will give it a try

 

with star diagnosis!

 

ah no i don't have that tool, i just wrench a little out of my garage

i was referring to the "sneaky ecu reset" with cycling the key. it surely can't replace a hard ecu reset, but i'll see if it helps at all

 

Now you have cleaned the throttle body, next clean the injectors, in a half tank of good fuel put 2 bottles of techron fuel injector cleaner, drive until below 1/4 tank then refill to half tank. This should help, at the mileage you have the injectors become gummed up and the atomization of the fuel is not perfect and will sometimes produce drops of fuel not a good spray pattern. This is more prominent when the engine is cold and could been seen as rough idle and shacking. Worth a try is it not.
Good luck

 

This/\/\ Try cleaning first and if that doesn't work call Serge at Benzworks, he's close to you.. I had a similar problem that the dealer was clueless about, turns out that I had 2 bad injectors that my indy figured out... It's either on the fuel side or the electrical so check that as well... Good luck...

 

I'll give this a shot, thanks.

 

check the ICV aluminum hose on the back of the supercharger make sure its fully pushed back in all the way. That will cause rough idle and even give you a check engine light.

 

Big thanks to Critter for the recommendation. Over the weekend I dumped in a couple bottles of Techron concentrate and since then there is no surging, and the throttle response, shifting, and supercharger engagement has become much smoother and crisper. In fact, I no longer have any supercharger chirp. I am amazed it has had such a profound effect on drivability! This combined with cleaning the TB has really made the motor come alive once again.

Since then, I have noticed there are some remaining vibrations (severity is much less) during startup and certain scenarios when driving. With how well the car is driving and idling now, I believe my problem may be worn motor and/or transmission mounts as they have not been replaced during the car's 97k miles. I'll be taking her into the shop in a week or two.

Hopefully my experience can be helpful to others who experience poor drivability with their AMG's!

-Ken