Things to check when have rough idle at start up in cold
Thread Starter
MBWorld Fanatic!
Joined: Aug 2015
Posts: 1,059
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From: DC Metro Area
2007 Mercedes E550
Things to check when have rough idle at start up in cold
Apparently it's common that the w203 has a rough idle at start up, especially in the cold. According to my research, the following are likely culprits:
1. $12 hose leak
2. Oil on cam sensors
3. Dirty MAF
4. Dirty throttle body
5. Bad O2 sensor
6. Spark plugs that need to be replaced
7. A unknown vacuum leak
8. Oil on Ecu connector
9. Dirty EGR valve
Can anyone think of anything else to check?? Top on my list is to do $12 hose, once I get the darn airbox off. Have already cleaned MAF, cleaned Thottle Body, checked fuel pressure, and replaced plugs. After doing the $12 hose, plan to clean cam sensors and do a smoke tear for leaks (will have to build or buy smoke machine..)
1. $12 hose leak
2. Oil on cam sensors
3. Dirty MAF
4. Dirty throttle body
5. Bad O2 sensor
6. Spark plugs that need to be replaced
7. A unknown vacuum leak
8. Oil on Ecu connector
9. Dirty EGR valve
Can anyone think of anything else to check?? Top on my list is to do $12 hose, once I get the darn airbox off. Have already cleaned MAF, cleaned Thottle Body, checked fuel pressure, and replaced plugs. After doing the $12 hose, plan to clean cam sensors and do a smoke tear for leaks (will have to build or buy smoke machine..)
Thread Starter
MBWorld Fanatic!
Joined: Aug 2015
Posts: 1,059
Likes: 73
From: DC Metro Area
2007 Mercedes E550
Apparently it's common that the w203 has a rough idle at start up, especially in the cold. According to my research, the following are likely culprits:
1. $12 hose leak
2. Oil on cam sensors
3. Dirty MAF
4. Dirty throttle body
5. Bad O2 sensor
6. Spark plugs that need to be replaced
7. A unknown vacuum leak
8. Oil on Ecu connector
9. Dirty EGR valve
Can anyone think of anything else to check?? Top on my list is to do $12 hose, once I get the darn airbox off. Have already cleaned MAF, cleaned Thottle Body, checked fuel pressure, and replaced plugs. After doing the $12 hose, plan to clean cam sensors and do a smoke tear for leaks (will have to build or buy smoke machine..)
1. $12 hose leak
2. Oil on cam sensors
3. Dirty MAF
4. Dirty throttle body
5. Bad O2 sensor
6. Spark plugs that need to be replaced
7. A unknown vacuum leak
8. Oil on Ecu connector
9. Dirty EGR valve
Can anyone think of anything else to check?? Top on my list is to do $12 hose, once I get the darn airbox off. Have already cleaned MAF, cleaned Thottle Body, checked fuel pressure, and replaced plugs. After doing the $12 hose, plan to clean cam sensors and do a smoke tear for leaks (will have to build or buy smoke machine..)
Thread Starter
MBWorld Fanatic!
Joined: Aug 2015
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From: DC Metro Area
2007 Mercedes E550
car has about 125k miles, and runs perfect after a few minutes to warm up. So disscinnecting the maf will put in open loop? If idle improves then the problem is the maf??
Junior Member
Joined: Feb 2015
Posts: 69
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From: Hermitage, PA
2004 C320 4Matic Sedan
Thread Starter
MBWorld Fanatic!
Joined: Aug 2015
Posts: 1,059
Likes: 73
From: DC Metro Area
2007 Mercedes E550
No unfortunately have not figured out the rough idle at cold start up. Changing plugs did help a lot though. I also really thoroughly cleaned the throttle body. This weekend I'm going to try to change the "$12 hose", since many have suggested this could cause idle problems .
Junior Member
Joined: Feb 2015
Posts: 69
Likes: 0
From: Hermitage, PA
2004 C320 4Matic Sedan
No unfortunately have not figured out the rough idle at cold start up. Changing plugs did help a lot though. I also really thoroughly cleaned the throttle body. This weekend I'm going to try to change the "$12 hose", since many have suggested this could cause idle problems .
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Thread Starter
MBWorld Fanatic!
Joined: Aug 2015
Posts: 1,059
Likes: 73
From: DC Metro Area
2007 Mercedes E550
Next on my list is
-$12 hose replacement (but having trouble getting stupid airbox off)
-Check and clean Cam sensors, which are the sensors in front of the camshafts in front of the engine??
-Smoke test with cigar
-Smoke test with homemade smoke machine
-Smoke test with $800 machine, which hoping to avoid :-))
Thread Starter
MBWorld Fanatic!
Joined: Aug 2015
Posts: 1,059
Likes: 73
From: DC Metro Area
2007 Mercedes E550
Thread Starter
MBWorld Fanatic!
Joined: Aug 2015
Posts: 1,059
Likes: 73
From: DC Metro Area
2007 Mercedes E550
$12 hose looked fine
Last night I checked the $12 hose and it looked fine. Actually the hose appeared to have been recently replaced- there was an aftermarket clamp on the deeper side of the hose. I traced my hands along the hose and did not see wear or leaks, and decided not to replace the hose since it looked good.
Last edited by LexBrett2; Dec 4, 2016 at 04:52 PM.
Thread Starter
MBWorld Fanatic!
Joined: Aug 2015
Posts: 1,059
Likes: 73
From: DC Metro Area
2007 Mercedes E550
Scotty Kilmer cigar smoke test
I tried the Scotty Kilmer cigar smoke test last night in hopes of finding a potential vacuum leak. Disconnected brake booster line a blew smoke into the engine. While smoke dos come out of intake, as expected, didn't see smoke leaking anywhere else. Perhaps there wasn't enough smoke or psi. My lungs hurt now. On to the next test in finding cause of rough idle in cold weather at start up!
Thread Starter
MBWorld Fanatic!
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From: DC Metro Area
2007 Mercedes E550
Cam sensors and Throttle body fine
Cleaned cam sensors and THrottle body thoroughly, to no avail. Maybe a little oil on cam sensors, but hardly detectable.
Junior Member
Joined: Mar 2015
Posts: 52
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2006 C230 Sport
Do you have a code-reader? I have the ELM327 and Torques app for my phone and it has worked pretty well I think.
I used it just after the episode where my 230/203 had rough idle and refused to start.
It couldn't give me a code because the check-engine light was not on, but the app did recommend I check the function of the EVAP, whatever that is.
I didn't pursue it further because at next start up everything seemed to be back to normal.
I did also have the Crankshaft position sensor replaced as well as the fuel pump last year. Two other things you might check on.
Best of luck.
I used it just after the episode where my 230/203 had rough idle and refused to start.
It couldn't give me a code because the check-engine light was not on, but the app did recommend I check the function of the EVAP, whatever that is.
I didn't pursue it further because at next start up everything seemed to be back to normal.
I did also have the Crankshaft position sensor replaced as well as the fuel pump last year. Two other things you might check on.
Best of luck.
Thread Starter
MBWorld Fanatic!
Joined: Aug 2015
Posts: 1,059
Likes: 73
From: DC Metro Area
2007 Mercedes E550
Do you have a code-reader? I have the ELM327 and Torques app for my phone and it has worked pretty well I think.
I used it just after the episode where my 230/203 had rough idle and refused to start.
It couldn't give me a code because the check-engine light was not on, but the app did recommend I check the function of the EVAP, whatever that is.
I didn't pursue it further because at next start up everything seemed to be back to normal.
I did also have the Crankshaft position sensor replaced as well as the fuel pump last year. Two other things you might check on.
Best of luck.
I used it just after the episode where my 230/203 had rough idle and refused to start.
It couldn't give me a code because the check-engine light was not on, but the app did recommend I check the function of the EVAP, whatever that is.
I didn't pursue it further because at next start up everything seemed to be back to normal.
I did also have the Crankshaft position sensor replaced as well as the fuel pump last year. Two other things you might check on.
Best of luck.
My next test is a more rigorous smoke test, but thanks for the tip on the crankshaft position sensor.
Thread Starter
MBWorld Fanatic!
Joined: Aug 2015
Posts: 1,059
Likes: 73
From: DC Metro Area
2007 Mercedes E550
Yeah I always use premium fuel, and use Royal Purple 5w-30 oil. What does marvel mystery oil do?
After I changed plugs and cleaned TB, the poor idle was greatly reduced.. suggesting something not sure what lol
After I changed plugs and cleaned TB, the poor idle was greatly reduced.. suggesting something not sure what lol
Junior Member
Joined: Mar 2015
Posts: 52
Likes: 0
2006 C230 Sport
MMO is an additive for both oil and fuel. I've never used it in the MB, but in other vehicles if I couldn't get a good idle I have mixed one third of the bottle with fuel and the rest into the oil. It is a marvel.
As to why it works? That's a mystery.
As to why it works? That's a mystery.
Junior Member
Joined: May 2016
Posts: 16
Likes: 1
C230K
What alleviated it for me is turning the ignition key to the "pre-start" position for a few seconds to let the fuel pump pressurize the system (you can hear it turn on, then off), THEN proceed with starting the engine. When I follow that protocol (on the cold starts), there is NO hesitation and the engine runs smoothly from the get go...
Try it out on your next cold start and let us know.
Last edited by AoxoMoxoA; Dec 6, 2016 at 06:11 PM. Reason: Clarification
Member
Joined: Oct 2007
Posts: 109
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From: Seattle
2002 G500, 1961 190b, 2001 SL500 Sport
The mystery is if it works, not why
Newbie
Joined: Dec 2014
Posts: 4
Likes: 0
From: Tunisia
W203 C180 Kompressor
I have the same problem on my W203 C180K.
I changed :
- Sparkplugs
- Coolant temperature sensor
- Thermostat
- Battery
And I cleaned the butterfly body.
The fault persists and is present only if the outside temperature in the morning is below 8 ° C
I changed :
- Sparkplugs
- Coolant temperature sensor
- Thermostat
- Battery
And I cleaned the butterfly body.
The fault persists and is present only if the outside temperature in the morning is below 8 ° C
Thread Starter
MBWorld Fanatic!
Joined: Aug 2015
Posts: 1,059
Likes: 73
From: DC Metro Area
2007 Mercedes E550
Update- used homemade smoke machine and found leak
Apparently it's common that the w203 has a rough idle at start up, especially in the cold. According to my research, the following are likely culprits:
1. $12 hose leak
2. Oil on cam sensors
3. Dirty MAF
4. Dirty throttle body
5. Bad O2 sensor
6. Spark plugs that need to be replaced
7. A unknown vacuum leak
8. Oil on Ecu connector
9. Dirty EGR valve
Can anyone think of anything else to check?? Top on my list is to do $12 hose, once I get the darn airbox off. Have already cleaned MAF, cleaned Thottle Body, checked fuel pressure, and replaced plugs. After doing the $12 hose, plan to clean cam sensors and do a smoke tear for leaks (will have to build or buy smoke machine..)
1. $12 hose leak
2. Oil on cam sensors
3. Dirty MAF
4. Dirty throttle body
5. Bad O2 sensor
6. Spark plugs that need to be replaced
7. A unknown vacuum leak
8. Oil on Ecu connector
9. Dirty EGR valve
Can anyone think of anything else to check?? Top on my list is to do $12 hose, once I get the darn airbox off. Have already cleaned MAF, cleaned Thottle Body, checked fuel pressure, and replaced plugs. After doing the $12 hose, plan to clean cam sensors and do a smoke tear for leaks (will have to build or buy smoke machine..)
While the car does run great once warm, the rough idle is maddening. This weekend I built a homemade smoke machine. It was easier than I thought and works well. I hooked up the smoke to the brake booster line and DID find a leak. The leak was coming from somewhere under the airbox, which I did not remove, so I will have to repeat the test once I have more time.
