WHY DOES MY CAR VIBRATE WHEN COLD???
Thread Starter
Junior Member
Joined: Feb 2015
Posts: 69
Likes: 0
From: Hermitage, PA
2004 C320 4Matic Sedan
WHY DOES MY CAR VIBRATE WHEN COLD???
Hi everyone, I've been chasing this problem for the last two years and really want to figure it out. If it is relatively cold outside or car hasn't been started in awhile, when I come to a stop with car in drive, it vibrates. It feels as if there is an excessive load on engine at this point. As I continue to drive it decreases and eventually comepletely goes away after about 5-7 mins. After I come up to a stop after 7 mins driving, no vibration. I've cleaned throttle body, replaced hoses, engine mounts, trans mount, everything. Could this be a fuel filter issue? Injector? I'm out of ideas. PLEASE HELP.
Newbie
Joined: Nov 2016
Posts: 11
Likes: 0
From: San Francisco, CA
Currently: 2005 C240 4matic wagon. Previously: 2001 C320 sedan.
Caveat: Most of my experience is not with MB products, it's with Jeeps. I'm just layman with three banana skills (on a good day) and far from an expert.
A few questions/clarifications:
Start with the cheap basics (which it sounds like something you've already done based upon your post). As engines age, they will start to idle a bit rougher as sensors get worn, etc. Rough idle can be caused by a lot of different things - sensors starting to go, carbon build-up in the engine, dirty fuel filter, dirty throttle body, old spark plugs, etc.
If I were you, I'd do the following:
Keep us posted on what works and what doesn't! It's frustrating to find threads of other people with the same problem as you but they never post what fixed their issue.
A few questions/clarifications:
- Does it sound like just a rough idle?
- When you say "cold" do you mean actually cold outside (e.g. <0 degrees Celsius) or when the engine just isn't warmed up to operating temperature?
- How many miles do you have on your engine?
- Are you up to date on all of your scheduled maintenance?
Start with the cheap basics (which it sounds like something you've already done based upon your post). As engines age, they will start to idle a bit rougher as sensors get worn, etc. Rough idle can be caused by a lot of different things - sensors starting to go, carbon build-up in the engine, dirty fuel filter, dirty throttle body, old spark plugs, etc.
If I were you, I'd do the following:
- Scheduled maintenance - replace the fuel filter if you haven't done so recently. Do the same with your spark plugs if they are coming up.
- Try running some fuel injector cleaner through your engine - I believe MB recommends Chevron Techron. You can pick it up on Amazon for $7-8. You may want to consider trying another product too - I'm very skeptical of "snake oil" products but I've tried Marvel Mystery Oil, Sea Foam and Berryman B12. My Jeep seemed to smooth out the best with MMO, I still skeptical though (placebo effect).
- I've performed this on my jeep before, never on a Merc, but you can try pulling your fuel injectors and cleaning them. It's pretty rare for modern cars to have fuel injectors go bad so you probably don't need to replace them. Unless you're getting an engine code, this may be more work than it is worth and the aforementioned cleaners might do just enough to knock any gunk loose.
- Not sure for your particular MB but, from my experience, a dirty IAC, MAF, or perhaps a MAP sensor could also cause a rough idle when cold. I'm sure when you cleaned your throttle body you also cleaned these sensors too. I've found that pulling the sensor and cleaning it manually works best (at least on my Jeep it did). Now that I think about it, I'm not sure if w203s have an IAC sensor (hopefully someone more knowledgeable will chime in and correct me). I saw no one had responded so I figured I'd give some friendly suggestions to start.
Keep us posted on what works and what doesn't! It's frustrating to find threads of other people with the same problem as you but they never post what fixed their issue.
Thread Starter
Junior Member
Joined: Feb 2015
Posts: 69
Likes: 0
From: Hermitage, PA
2004 C320 4Matic Sedan
Caveat: Most of my experience is not with MB products, it's with Jeeps. I'm just layman with three banana skills (on a good day) and far from an expert.
A few questions/clarifications:
Start with the cheap basics (which it sounds like something you've already done based upon your post). As engines age, they will start to idle a bit rougher as sensors get worn, etc. Rough idle can be caused by a lot of different things - sensors starting to go, carbon build-up in the engine, dirty fuel filter, dirty throttle body, old spark plugs, etc.
If I were you, I'd do the following:
Keep us posted on what works and what doesn't! It's frustrating to find threads of other people with the same problem as you but they never post what fixed their issue.
A few questions/clarifications:
- Does it sound like just a rough idle?
- When you say "cold" do you mean actually cold outside (e.g. <0 degrees Celsius) or when the engine just isn't warmed up to operating temperature?
- How many miles do you have on your engine?
- Are you up to date on all of your scheduled maintenance?
Start with the cheap basics (which it sounds like something you've already done based upon your post). As engines age, they will start to idle a bit rougher as sensors get worn, etc. Rough idle can be caused by a lot of different things - sensors starting to go, carbon build-up in the engine, dirty fuel filter, dirty throttle body, old spark plugs, etc.
If I were you, I'd do the following:
- Scheduled maintenance - replace the fuel filter if you haven't done so recently. Do the same with your spark plugs if they are coming up.
- Try running some fuel injector cleaner through your engine - I believe MB recommends Chevron Techron. You can pick it up on Amazon for $7-8. You may want to consider trying another product too - I'm very skeptical of "snake oil" products but I've tried Marvel Mystery Oil, Sea Foam and Berryman B12. My Jeep seemed to smooth out the best with MMO, I still skeptical though (placebo effect).
- I've performed this on my jeep before, never on a Merc, but you can try pulling your fuel injectors and cleaning them. It's pretty rare for modern cars to have fuel injectors go bad so you probably don't need to replace them. Unless you're getting an engine code, this may be more work than it is worth and the aforementioned cleaners might do just enough to knock any gunk loose.
- Not sure for your particular MB but, from my experience, a dirty IAC, MAF, or perhaps a MAP sensor could also cause a rough idle when cold. I'm sure when you cleaned your throttle body you also cleaned these sensors too. I've found that pulling the sensor and cleaning it manually works best (at least on my Jeep it did). Now that I think about it, I'm not sure if w203s have an IAC sensor (hopefully someone more knowledgeable will chime in and correct me). I saw no one had responded so I figured I'd give some friendly suggestions to start.
Keep us posted on what works and what doesn't! It's frustrating to find threads of other people with the same problem as you but they never post what fixed their issue.
