Sorry guys for posting here - but I posted to the S55 section, not much response, and was told there maybe someone here who has the answers: (I really need someone's help)

I have a 2004 - S55 amg and in the past 3 or 4 weeks all of a sudden it is running like crap. And in the past 3 or 4 days it is really running rough.

I took it to the dealership and they acknowledged that it was not running well, said that there were no codes present and suggested the following:
a) flush the tranmission oil
b) replace the engine and transmission mounts (they said that they notice extra vibrations)
c) replacing the spark plugs.

I have not had them do any of the above. I just paid for them to look at it first. But none of them except the spark plugs makes sense.

The issues is that for awhile, every 3 or 4 months, there will be a period of time that the engine seemed to have misfired. It was not like I would hear a misfire, but the when I would press on the gas the acceleration would be not be smooth and it will be like kicking in and out. the dealer at the time said that I should just add techron to the gas to clean the fuel or fuel line

but now I hear a hissing noise and the engine is really running rough.

When i drive, the acceleration seems to have a hesitation and there seems like something is actually slowing the engine down. like in the old days when you have something stuck in the wheel of the bicycle.

When in idle there is some knocking noise coming from the engine ... not too much but a little ... actually someone the other day asked if my car was diesel (it is gas :-)

Can someone here help ?

I hate to spend a lot of money at the dealer for them just tell me it is somethign else. It has happened with my S500 and it was just a big waste.

The engine oil seems to be a bit darker than normal although i just changed it 4000 miles ago with Mobile 1. I am hoping that the shop actually changed my oil and filter since they charged me :-)

Thanks guys ---

I am pretty new to this forum but just found it as i was searching for answers.

 

Sounds like the exact same symptoms mine once had. It turned out to be a slightly frayed ignition lead. A set of new leads and spark plugs and she was brand new again.

 

thanks - i will try that - hopefully it will fix it - will post results here.

 

Part of how you described the problem almost sounds like a very sick IC pump. It's another cheap/easy part to replace, and if you have never had it done, I would think that there is a good chance that is at least part of the problem. The engine knocking is another issue, but if it's more of a ticking than knocking sound, it could be normal.


Good Luck

 

IME, Hissing Noise + Rough Engine usually = Vacuum Leak

I know nothing about the vacuum system on the 211 though, so I wouldn't know where to tell you to look.

 

I agree. Hissing noise is almost certainly a vacuum leak somewhere. The beauty of that is that even though you might not have intimate knowledge of that specific vac system, you can usually just follow the hissing noise with your ear and find the culprit.

If you are mechanically inclined, it wouldn't hurt to take the plugs out and check em, also to make sure the plug wire boots are snapped onto the plugs tightly.