94 s320's rpm goes up and down when hot

Jun 10, 2008 | 11:15 AM

my_galaxy

Thread Starter

Junior Member

Joined: Mar 2008

Posts: 30

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94 mercedes s320

94 s320's rpm goes up and down when hot

hi guys
i have a 94 s320, when i start in the morning it starts fine but when i drive around and stop on the light or just put it in the parking, engine's rpm start going up and down and sometimes it shuts down. but if i keep my foot on the accelerator just little bit then rpm stays normal.
can anyone help please?
thanks

Jun 12, 2008 | 01:59 AM

OdinsThrone

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Joined: Feb 2008

Posts: 22

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1998 S500

I have a 98 S500 that does the same thing but it does not die. Mine jumps from idle 700 rpms to about 800 back to idle.

Jun 12, 2008 | 09:34 AM

Rod Spohn

Senior Member

Joined: Apr 2004

Posts: 393

Likes: 2

From: Mesa, AZ

2011 E350 Bluetec, 1996 S320 & 2006 E320 CDI Sold to my son & 2017 GMC 2500 Diesel Pick up

I had the same problem with mine a couple of years ago. It ended up being the fuel regulator. This is a fairly inexpensive part ( about $90)and easy to fix – about 15 minutes. It is located on the right top front of engine. One way you can tell if it’s going bad is to pull the Vacuum line off and smell it. If you see or smell gas it’s bad. The diaphragm starts letting gas seep by. Hope this helps

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