Orkhan Mammadov

Hi, I am driving 2002 E320. Engine is shaking when idling (poor combustion/rough idle) in P, R, N and D. When I give a little throttle and rev engine up to 700-900rpm (or higher) problems goes away. So at traffic light I hold brake and give a slight throttle (100rpm higher) and vibration gets lost. Also, while driving engine works very well and there is no shaking nor sings of poor combustion.
I have checked combustion at cylinders and computer shows everything is ok. Spark plugs are new, injectors recently cleaned, and there is no significant error in the scanner that could give a hint. The only error was catalytic sensors and I changed all four of them which obviously didn't help.
When I shift gears from N to D or R transition is very smooth and shaking doesn't gow away or lessen in N compared to D. So problem doesn't look like to be engine or transmission mounts to me.

What else could cause poor/rough idling problem?

EGR? throttle body? which other parts or sensors?

Please advise,
Orkhan

Bahnstormer

Motor mounts?

F1Fan

Perhaps vacuum leak or extra air getting into the system? Engine mounts are very easily torn or worn out. You are very sure they are not torn? The mounts are liquid filled and a small tear could have let the liquid out. If you put the car in D, and hold the brake, then give a little gas, does the engine move at all? New mounts will have very little movement, while torn mounts will show the engine trying to jump out of the engine bay.

Strigoi

Agreed.

tjts1

Or trans mount.

*toxic*

i have a w210 but mine does the same thing im having a guy who works on them all the time come to look at it next week but mine does that exact thing you described to a t so what i have found os that there may be a leak in the vacuum advance system and can cause a shake at idle and it to idle rough or have a abnormal sound when run hipe this helps

charlesb2003

I just recently spent a fair amount of time and money chasing the same problem as you on my 05 E320. Changed all the spark plugs, camshaft position sensor, crankshaft position sensor, valve cover gaskets, PCV hoses, re-sealed PCV chambers, changed air filters, cleaned MAF sensor, ran multiple bottles of injector cleaner, still had that exact same vibration. Glad I did all of that as preventative maintenance, but was really bummed out that it didn't fix the vibration.

Changed engine and transmission mounts, smooth as silk. The old mounts had collapsed and were very stiff, they were not loose at all when I revved the engine with my foot on the brake in drive so that's why I didn't think it was that, but it was. From what I've read they are prone to failure. Just go ahead and change them, they are the most likely culprit of your issue.

bernard farquar

1) 02 e320 would be a w210, different forum.

2) Catalyst sensors? I'm going to assume you mean O2 sensors, and if you changed all four, to no avail, you might have plugged up converters, which sill get worse over time, until they cause misfire codes and throw you into limp mode.

TechSurfer

A dirty throttle body shutter & dirty idle air control are very common causes of rough idle, especially when the car drives normally and no check engine light or DTCs appear.

Broadly speaking, you can easily decide if the issue is the engine itself or the mounts in the following manner. First of all, does the needle on RPM occasionally dip at all, even slightly, at idle? Next, with car idling in "Park," place your ear close to each tailpipe. Does the putter of the engine sound perfectly smooth? Up to one sputter/misfire every ten seconds is exceptable, more are not. Lastly, place your hands firmly on the plastic cowling of the engine at idle and feel for any intermittent shake of the engine. Any of these indicators will point to a misfiring engine that will cause a perceivable shaking; the absence of any misfire points to engine/transmission mounts.

bakhtyar khan

Ive researched on this issue (poor idle) quite extensively extensively and have found that the egr valve located at the back of the engine, located left of the throttle body causes the issue of rough idle due to a closed valve which causes disruption in the recycled airflow from the air intake. This issue generally affects m112 and m113 engines as both my w220 s350 and w211 e240 had devoleped this issue of stuck egr valve that caused poor idle and changing the entire egr valve helped fix the poor idle