# 1993 Mercedes 300e bad idle

**URL:** <https://community.cartalk.com/t/1993-mercedes-300e-bad-idle/27117>\
**Category:** Maintenance/Repairs\
**Created:** [March 1, 2009, 12:28am UTC](https://community.cartalk.com/t/1993-mercedes-300e-bad-idle/27117 "2009-03-01T00:28:02Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![MrBenz](https://avatars.discourse-cdn.com/v4/letter/m/e0b2c6/32.png) [@MrBenz](https://community.cartalk.com/u/MrBenz)\
**Post date:** [March 1, 2009, 12:28am UTC](https://community.cartalk.com/t/1993-mercedes-300e-bad-idle/27117/1 "2009-03-01T00:28:02Z")

</div>

I recently bought a 1993 Mercedes Benz 300e from a private seller, it has 190xxx miles on it. The car runs good but when it is stopped the rpms drop below 900 and it has a very noticable vibration which goes away when I accelerate. There is no smoke or signs of an oil leak but there is a mild smell of something burning (especially hwne your behind the car). Anyone have an idea of what this could be?

---

<div class="post-metadata">

**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\
**Post date:** [March 1, 2009, 12:50am UTC](https://community.cartalk.com/t/1993-mercedes-300e-bad-idle/27117/2 "2009-03-01T00:50:26Z")

</div>

The first step should be running a compression test as one low cylinder can cause a symptom like this. Hopefully the compression will be fine and the problem will be comparatively minor; ignition components, vacuum leak, etc.

The reason for the compression test is to weed out a mechanical fault as it is very easy to throw a fortune in parts at a problem like this and never resolve it.

---

<div class="post-metadata">

**Author:** ![mcparadise](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mcparadise/32/32_2.png) [@mcparadise](https://community.cartalk.com/u/mcparadise)\
**Post date:** [March 1, 2009, 1:48am UTC](https://community.cartalk.com/t/1993-mercedes-300e-bad-idle/27117/3 "2009-03-01T01:48:10Z")

</div>

Normal idle speed for most cars these days is about 700-750 RPM. Why do you want this engine to idle at 900 or more?

In addition to ok4450’s recommendations, which I agree with, as always, you might want to look at the Idle Air Control (IAC) valve, and associated parts/systems.

I hope you have a working relationship with an independent mechanic who knows MB cars.

---

<div class="post-metadata">

**Author:** ![MrBenz](https://avatars.discourse-cdn.com/v4/letter/m/e0b2c6/32.png) [@MrBenz](https://community.cartalk.com/u/MrBenz)\
**Post date:** [March 1, 2009, 4:18pm UTC](https://community.cartalk.com/t/1993-mercedes-300e-bad-idle/27117/4 "2009-03-01T16:18:07Z")

</div>

Thank you ok4550 & mcparadise. I will have my mechanic take a look at it.

---

<div class="post-metadata">

**Author:** ![MrBenz](https://avatars.discourse-cdn.com/v4/letter/m/e0b2c6/32.png) [@MrBenz](https://community.cartalk.com/u/MrBenz)\
**Post date:** [March 1, 2009, 4:19pm UTC](https://community.cartalk.com/t/1993-mercedes-300e-bad-idle/27117/5 "2009-03-01T16:19:54Z")

</div>

Oh yes I did fail to mention in my first post that sometimes when I start the car to let it warm up it will do its normal vibrations, rpms drop and it will stall (its an automatic trans.)