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1994 E220 Coupe
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337 Posts
Discussion Starter · #1 ·
Hey guys,
Got a '94 E220C and when I have it in D and stopped (ie, at traffic lights with the brake depressed) the idle is really low and there is noticable vibration. Usually I put it into N and then back in D when I need to take off.

The idle in P or N seems fine (around the 800-850 mark) and is smooth, it's just when it's in gear which the problem arises.

Does anyone have any knowledge or experience with such an issue?
My initial thought was something with the oil pressure and torque converter? The gearbox oil was changed some while back and I don't think the problem appeared after the oil change

Help is greatly appreciated
 

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2005 W215 CL500
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3,924 Posts
Strangely my problem is the opposite of yours, smooth in D but rough in N or P. For me it's probably engine mounts, for you trans mounts??
 

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1,749 Posts
I have a similar idle problem, but only on rare occasion, and only when the engine doesn't fire the first couple of times I turn the key.

It's 100% my fault for not letting the engine catch, but I can't stand to hear engines/starters protest when they're keyed too long.

Usually, a stab at the accelerator pedal gets everything in order, and the 'check engine' light goes out. What amazes me, is the engine remains running while in-gear, and is remarkably smooth, while idling at what can't be more than 250 RPM...if that.

Is the 'check engine' light coming on? The gearbox oil shouldn't matter, unless it was filled with 90W-140. There may be an idle compensating device, usually used for adjusting for A/C compressor drag, which may be at fault, but I can't imagine putting it in -gear gets the compensator to do anything.

I'll keep a few brain cells on it.
 

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1994 E220 Coupe
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337 Posts
Discussion Starter · #4 ·
The car itself only has 58,000 miles and is taken care of well.

I do know however, that the engine mounts are gone, and possibly the gearbox mounts. I understand this would cause NVH but not the low idle.

Where should the 2.2L 94 model with 4 speed automatic idle in P and D if anyone knows?

Also, on the topic of the gearbox, it has a S and E (standard/economy) switch. I've toggled between the settings and even though the E is meant to change gears earlier etc, I haven't noticed the slightest of differences in the two settings. Is this just a gimmick that never did anything?
 

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W124 400E, W126 500SE
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971 Posts
depends on what you mean by low idle... I had about 500RPMs on my E320 while in D, and it caused no problems.
 

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1987 W124 260E - 2003 W209 CLK270 - 2007 CLS Brabus
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119 Posts
Rotary idle valve is just for this..
It is electronically controlled via the ECU and maintains a steady idle with differing loads..

Check it out.. it may need cleaning as it can get a little sticky
 

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Mercedes 1986 300E 165,000 miles
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110 Posts
I have been having the same problem with my 86 300E with 137K miles but mine stalls in intersections and stop and go traffic. Its fine on P and N but does idle on the rough side. I'm planning to check the EHA and OVP relay this weekend. Can a slapping timing belt cause this?
 

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1994 E220 Coupe
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337 Posts
Discussion Starter · #8 ·
Rotary idle valve is just for this..
It is electronically controlled via the ECU and maintains a steady idle with differing loads..

Check it out.. it may need cleaning as it can get a little sticky
Any write up on how to do this?
I take it that it's on the throttle body?

If it helps, turning the AC on doesn't raise the idle like on other cars
 
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