Runs rough when cold
Thread Starter
Junior Member
Joined: Jul 2005
Posts: 33
Likes: 0
2001 E320 4 Matic 174,000 miles
Runs rough when cold
I have a 2001 E320 4matic with 105,000 miles. It starts and idles fine when cold. When I initially take off everything seems to be ok. When I drive a couple of blocks and come to a stop sign it idles rough and hesitates and almost dies upon taking off. After that it runs just fine. Once it is somewhat warmed up everything is ok. Anyone have any ideas on what may be wrong. I was thinking maybe the oxygen sensors,but I am not sure. Thank You in advance
Newbie
Joined: Jul 2003
Posts: 19
Likes: 0
From: Boston
1998 E320 4Matic
I have a '98 E320 4matic and it does exactly the same thing. Ok on start up, runs rough at first stop sign, almost stalling when pulling out, and then fine. 
Interested to see if any one has any ideas or similar problem. I thought I was the only one as I have never heard of this one before.
Interested to see if any one has any ideas or similar problem. I thought I was the only one as I have never heard of this one before.
Thread Starter
Junior Member
Joined: Jul 2005
Posts: 33
Likes: 0
2001 E320 4 Matic 174,000 miles
I noticed it missed a couple of times yesterday when I came to a stop and idled for a few minutes. I changed the fuel filter once. I was thinking I would change it again. I was cosidering changing the spark plug wires. It seems like a spark miss. I changed the plugs @ 80,000 miles. I took the car to Auto Zone and had them use their hand held to read default codes, there weren't any. The check engine light has never come on. I would take it to the dealership but I am not sure that they will be able to figure it out unless it is misfireing at the time.
Newbie
Joined: Nov 2005
Posts: 17
Likes: 0
From: pennsylvania
1998 e 320 4matic,2001 e320 4matic wagon, 1990 Carrera 2
Runs rough
I had the same problem on my 98 E320 4matic(137,000 miles) and I thought it was a mass air sensor going bad. What it turned out to be was the intake was not properly sealed at the junction of the mass air sensor. I must have tweaked it when I checked my air filter. Once I sealed everything back up, the car ran fine. Just something to check, as the connection can be tricky to seal up properly.
Newbie
Joined: Jun 2006
Posts: 9
Likes: 0
2001 E320W4
I had the same problem on my 2001 E320 4matic (87,000 miles).
Running rough in the morning, when idling, and hesitating when taking off.
Took it to my dealer and it turned out to be carbon buildup in the engine. In addition to three separate gasoline treatments, they had to perform a top engine clean procedure. Basically added a component to the engine directly, let it sit for several hours, and then drove in third gear to heat up engine and blast out the carbon. Runs like new again except for the damn steering wheel squeak which comes back here and there.
This was after replacing sparks plugs, replacing fuel injectors, replacing spark wires, 60,000k service, and 100,000k service, replacing a faulty sensor because of rough idling and check engine light coming on with misfire codes on the injectors....Carbon buildup was noticed once service tech got into replace the injectors. They noticed a crazy amount of carbon on the back of the valves.
Always buy premium gas and run chevron techron through about every 5,000 miles, but still got the carbon buildup............
Running rough in the morning, when idling, and hesitating when taking off.
Took it to my dealer and it turned out to be carbon buildup in the engine. In addition to three separate gasoline treatments, they had to perform a top engine clean procedure. Basically added a component to the engine directly, let it sit for several hours, and then drove in third gear to heat up engine and blast out the carbon. Runs like new again except for the damn steering wheel squeak which comes back here and there.
This was after replacing sparks plugs, replacing fuel injectors, replacing spark wires, 60,000k service, and 100,000k service, replacing a faulty sensor because of rough idling and check engine light coming on with misfire codes on the injectors....Carbon buildup was noticed once service tech got into replace the injectors. They noticed a crazy amount of carbon on the back of the valves.
Always buy premium gas and run chevron techron through about every 5,000 miles, but still got the carbon buildup............
Trending Topics
Thread Starter
Junior Member
Joined: Jul 2005
Posts: 33
Likes: 0
2001 E320 4 Matic 174,000 miles
I replaced the fuel filter and I still have the problem. I talked to a Mercedes indy yesterday and he told me to run Chevron gas in it and see what happens. He said there isn't a common thing to cause this problem. I did get the feeling from him that it has something to do with buildup in the fuel system ie, injectors or carbon build up. I did ask him if he thought the spark plug wires could be bad. He said usually when they are bad you get a check engine light on. I did tell him I changed the spark plugs at 80,000 miles. So, now I am running a strong mixture of techron. The car seems to be idleing smoother while warm. I will see what happens when it is cold today. I will run the additive for a few tanks of gas and see what happens. I have always ran 76 gas and a fuel additive every so often so I would not have a builup problem. 76 gas seemed to run better in the car than the others and it is supposedly a top tier fuel. I will keep everyone informed.
Last edited by dnewman007; Nov 1, 2006 at 09:30 AM.
MB World Stories
The Best of Mercedes & AMG
6 Mercedes Models That Did NOT Age Well (But Are Somehow Still Cool)
Verdad Gallardo
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun
Verdad Gallardo
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Verdad Gallardo
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
MBWorld Fanatic!
Joined: Sep 2005
Posts: 6,191
Likes: 242
From: Albuquerque
'10 CL550, '12 GL550
Remember when cars had chokes?
Even today an engine needs a richer mixture to run correctly when cold.
There are special subsystems to accomplish this, including items such as temperature sensor, cold start injector, idle control valve, etc.
If it's not running right cold but runs fine warm, it's a problem with this system. Or a vacuum leak.
It's sheer wishful thinking and simply guessing to think this has anything to do with fuel filter.
Even today an engine needs a richer mixture to run correctly when cold.
There are special subsystems to accomplish this, including items such as temperature sensor, cold start injector, idle control valve, etc.
If it's not running right cold but runs fine warm, it's a problem with this system. Or a vacuum leak.
It's sheer wishful thinking and simply guessing to think this has anything to do with fuel filter.
Thread Starter
Junior Member
Joined: Jul 2005
Posts: 33
Likes: 0
2001 E320 4 Matic 174,000 miles
I noticed over the weekend that the car missed a couple of times when it was warm after stopping at a stop sign/light. It has not missed since than while warm only after the initial start up, and after driving a couple of blocks to a stop sign. Upon starting it in the morning, it starts fine, idles up to about 800-900 rpm than settles down to about aprox 600 rpm. Everything in the cold start system seems to be working correctly. I appreciare the input everyone is giving me. Thank You!
Thread Starter
Junior Member
Joined: Jul 2005
Posts: 33
Likes: 0
2001 E320 4 Matic 174,000 miles
After extensive research I ran some top engine cleaner through the master cylinder vacume line into the top of the engine. It appears the problem is solved (I'm keeping my fingers crossed). It has not idled rough since. As a matter of fact the car idles smoother and has more power/torque when taking off from a dead stop. I hope the car continues to run like this for a long time.
