JoeBonner

Just Read a post "2003 E320 base model, bad idle". My E320 starts ok but after driving it for a while (10-15 minutes), when I come to a stop, it idles pretty rough. Last night after dropping off my wife and daughter, I drove to a fast food drive up. While waiting, the car was idling roughly. I put it in park - no change. I tapped on the accelerator. The RPMs fluctuated around 2000-2200 for quit some time. Then it came down to normal but was still rough. Does anyone have any thoughts on this?

joseph-aaron

Mine does that to pretty much everyday somethimes it just shuts off but cranks back fine. I asked same question find out anything will let ya know. If I forget follow my posts. Mines a 04 e320. Mine does that mostly when driving. Stuck in traffic, stop lights..etc..

Toastr

So it seems fine when driving, but it vibrates a lot at idle? Is it when the car is in gear only?


It seems that these cars (or mine, at least) tend to like to eat up motor mounts near the transmission. That often will cause vibration at a stop. FWIW, my car has had 3 replaced before I owned it, and I'm currently at 83k miles.

Lots of posts around here that will help you diagnose it if that's the issue, I'd say start there first.

S70Houston

Sounds like motor/transmission mounts to me as well. I had a very similar issue, had both motor mounts and the transmission mount replaced and the car drives like new again.

Islandgirl_ig

Could be caused by cracked and/or shredded driveshaft flex discs, resulting in excessive driveshaft movement.

joseph-aaron

Not sure if helps but sounds the same. In the morning I let it warm up it runs fine. Theres times at stop and start, red lights, stop signs it goes strange. RPM goes crazy might shut off. As far as mine its a low idle problem. Had a local "expert" tune it up never had that problem again.

cstevenson

I've got this problem on my 2004 CLK. A throttle reset fixed the problem for a month or so, but now it's back and worse... any resolution?

cougit25

I read here about the air filter housing not being seated properly on the throttle bore/MAF due to defective clips. So at idle, extra air seeps into the bore disturbing the MAF's air flow readings. Over time the clips which hold the housing in place get bent and no longer hold it in place properly.

Cheers

cougit25

• #2
  
  gafitanu , 03-06-2017 06:54 AM
  What do you mean by "they didn't put the air intake back on the engine"? Is it the 2 plastic tubes from the air intake cover or the entire air cover that contains the 2 air filters? Make sure the big air intake latches correctly on all 4 metal clips. Check them, sometime if they are not pressed carefully they bend and do not latch on the rubber posts. This allows "false" air to leak into the throttle body, the MAF gets discombobulated and gives rough idle at stops (ask me how I know). If you still have rough idle then it's on to MAF replacement and there are a ton of posts on this subject (most of them on the C class section).
  When you discovered the intake in the trunk you should have taken the car back, bring the service manager and make a loud scene (peppered with profanity) in front of others.
  You may get on their "no soup for you" list but I am sure there are other dealers in LV.
  The SBC recall is not really a recall it's a 10 year warranty extension but yours is gone. Do you have errors from the SBC?
  

gafitanu

Just to clarify here.
Vibration at idle is different than rough idle.
I believe the OP mentions several times rough idle and not once vibration.
Rough idle means that the idle RPM is fluctuating randomly almost stalling sometimes. The ECU will compensate temporarily avoiding stalling but the cause is still there. Many times the cause for the rough idle is the MAF sensor that needs cleaning or replacing. As I posted on another thread when I pulled the air box to check the MAF I turned it upside down and I saw a bent clip. Instead of locking on the rubber mount it was sitting on top of it creating a gap of approx. 1/2" between the air box mouth and the throttle. I corrected the clip and the rough idle disappeared.
Vibration (because I had that too) which is continuous and consistent (more profound when stopped while in drive) is most likely caused by the engine mounts. Use only OEM or Lemforder.

EuroDriverSD

Does the rough idle/rpm fluctuation happen when you are stepping on the brake pedal? If so, you probably have a vacuum leak - I would start by looking at the vacuum hose going to the brake booster. Might be the brake booster itself that is failing.

cmriv

egr valve maybe sticking or a fuel pressure issue possibly. And agree, OP can you clarify, vibration at idle or is the idle itself suspect/fluctuating?

EuroDriverSD

I just resolved this issue on my W203. Rough idle, worse at full operating temperature on hot days. When I would apply brakes firmly, it would sputter and nearly stall out.


Changed MAF, problem solved. I have also read the brake light switch can cause this issue but personally I haven't experienced it.


I still have vibration while in gear - motor and transmission mounts are next in order.