hydeaway

Recently in the past couple of weeks the car has been a little rough during idle. Not just during cold start but even after a long drive. At first i thought it was the ECU learning the cold / and not cold weather temp in chicago. The car has the K2 upgrade but i dont think thats the reason for the rough idle. Any advice from the experts would be appreciated. Thanks.

jamusa

First chech to see if the ECU plugs are all the way in........if the center pin is not snug ,you will get a rough idle.

hydeaway

I will check once i get home. I forgot to mention i also have the Renntech lowering module. That shouldn't make a difference since all (lowering module and K2) was installed months before i got this issue...?

dsc

I have K2 and the Renntech lowering module also. My idle has been rough for a long time. I have had the car checked by multiple shops and had the plugs changed. Mercedes said it was normal, that most E55s do it and that the ECU is constantly analyzing and making changes so that the rpm will fluctuate some at idle. The idle isn't super rough but the car jiggles slightly. It's not like you can't tell the car is running.

hydeaway

That's exactly what mine is doing. But i dont remember it being like this a month ago.

chiromikey

mine behaves similarly and does seem to have been worse lately. could be the winter gas i dunno...???

hydeaway

Interesting!

dsc

Mine does it is summer also.

Finny

Check the vacuum hose underneath the right hand side air filter box. (standing in front of car) Crank case ventilation hose. This can pop out some times which causes the same symptoms as described. Can also cause phantom acceleration.

Let us know how you went...

Grumpy666

A rough idle can also be caused by an O2 sensor starting to fail. Can you data log, looking at bank1/sensor1 and bank2/sensor1?

newton22

Bad MAF, plugs, wires?

Grumpy666

No MAF - it's Speed Density.

hydeaway

Checked vacum hose and it looks pretty secure.


ECU is also pretty secure.

hydeaway

Here's the update..... Took the car to Knauz MB dealer (also kleemann dealer). Told my SA that the car has the K2 installed and he said OK no problem we wont touch anything on the ECU. I was like "cool" just let me know if you find any issue with the car. Went to work few hours later my SA called and said that they cannot get any error reading from the ECU because of the K2 software. Now he's ranting about that my car is no longer under waranty because of all the stuff done to the car - yad yada..... I told him i will call him back after i think this through. I then called cory at kleemann and explained my situation (cory is such a nice guy). He suggested to get the ecu flashed back to stock since i have not done my injector recall and ecu flashed. I then called my SA supprisingly he was cool about doing the recall work since my car is no longer under "waranty"..... Now back to stock ECU and still cant get any error codes. My SA suggested we should do a compresion test because there might be a bent rod or something going on internally (which he wants me to pay out of pocket). I explained to him that the car has not lost any power and everything seems to be working other than the rough idle. Anyway, I took the car back and going to send my ECU back to cory to get it reprogram.

Sorry for the long post figure someone might want to know if they have the same issue.

By the way I hardly drive my car fast I just like to know that i can... and cory mentioned hes never seen any E55 with a bent rod before....

chiromikey

lol, that's funny...the only symptom is rough idle and he came up with a bent rod.

Jakpro1

My rough idle was vacuum line back of the motor that came loose. It was tricky to see as it looked connected, but had just popped straight back.

hydeaway

can you elaborate where that vacum hose is located? maybe take a pic. thanks

vader

Does it get better when warmed up to operating temp ? Mine gets a little rough when its a cold start sometimes. It may be a little rich at cold start if you had your ECU upgraded

hydeaway

Its the same during cold start and after a drive.

mclarenm8d

I'm thinking you should get a second opinion ... PM me if you wish, the guys that work on my CL55 at MB of Hoffman Estates might get you better answers ... or at least, wouldn't give you the racket talk about warranty.

Almost forgot to mention - the technician can adjust the in-gear and out of gear idle. My idle is REAL rough, because I requested to have my idle set down low (I'll occasionally see a 4xx on the digital readout).

My experience with bent rods is that they don't improve matters as the RPM goes up. For someone to just spout-off "bent rod" to you seems kinda jumping to the expensive problem and sloppy analysis.

hydeaway

Thanks for the offer. I actually have another appointment later this week from another MB dealer. If i get the same service I will accept your offer. Thanks again.

DChan415

Rough idle on my car was due to a vacuum leak. My car is under warranty and the dealer could never find the problem. We only resolved the issue after we had to replace the intake manifold gaskets ourselves during another unrelated repair.