Things to check when have rough idle at start up in cold
12-15-2016, 08:47 AM
#26
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2007 Mercedes E550
Preliminary Smoke test
I built my most excellent smoke machine and conducted test this weekend: Hooked up to brake booster line, covered intake, and smoke poured out somewhere under the box.
Since I could not locate the exact location of the leak, so the Next step is to remove intake box and look at hoses. I suspect one of those nasty vacuum lines are leaking. I'm Also hoping to fully remove airbox, and bought special tools to make it happen. It also be a leaking intake manifold gasket, which is a pain but seems doable. Stay tuned..,
Since I could not locate the exact location of the leak, so the Next step is to remove intake box and look at hoses. I suspect one of those nasty vacuum lines are leaking. I'm Also hoping to fully remove airbox, and bought special tools to make it happen. It also be a leaking intake manifold gasket, which is a pain but seems doable. Stay tuned..,
12-15-2016, 12:40 PM
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2004 C320 4Matic Sedan
I built my most excellent smoke machine and conducted test this weekend: Hooked up to brake booster line, covered intake, and smoke poured out somewhere under the box.
Since I could not locate the exact location of the leak, so the Next step is to remove intake box and look at hoses. I suspect one of those nasty vacuum lines are leaking. I'm Also hoping to fully remove airbox, and bought special tools to make it happen. It also be a leaking intake manifold gasket, which is a pain but seems doable. Stay tuned..,
Since I could not locate the exact location of the leak, so the Next step is to remove intake box and look at hoses. I suspect one of those nasty vacuum lines are leaking. I'm Also hoping to fully remove airbox, and bought special tools to make it happen. It also be a leaking intake manifold gasket, which is a pain but seems doable. Stay tuned..,
12-15-2016, 01:31 PM
#28
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2007 Mercedes E550
Rough idle starts at 50 degrees C
Noticed that my rough idle doesn't really start until about 50 degrees C. On my list is changing the coolant temp sensor, which this may suggest??
12-15-2016, 01:33 PM
#29
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2007 Mercedes E550
I was affected by the same phenomenon and did the whole checklist thing which produced nothing awry, although my gut told me it was a fuel-related issue.
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.
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 LexBrett2; 12-15-2016 at 03:40 PM.
04-10-2017, 03:11 PM
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AMG GTS
Did you ever figure this out, LexBrett2? I have been researching a bit on the forum for my '03 C230K rough idle and stumbled upon a M112 solution. Curious if you stumbled on the same and tried replacing the EGR valve.
The solution I'm referencing is Post #22 in this thread: https://mbworld.org/forums/c-class-w...12-engine.html
The solution I'm referencing is Post #22 in this thread: https://mbworld.org/forums/c-class-w...12-engine.html
04-11-2017, 05:02 AM
#31
With the new fuel filter, the car powers right up at start, even on frigid mornings; no rough idle.
Hope this helps.
04-11-2017, 07:10 PM
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AMG GTS
I brought it into the shop today to do a tranny fluid/filter change and my mechanic popped in a scanner to see what codes have come up in the system. Looks like code "201D-001" has come up with 47 frequencies. He believes it may be a clogging catalytic converter based on this code. Curious if anyone on here has experienced having this code and if swapping out a cat converter led to resolving rough idles?
04-11-2017, 10:16 PM
#34
Thank you AoxoMoxo! I actually changed the fuel filter about 40k miles ago - hopefully its lifespan is longer than this as the original one was swapped out at 88k miles as preventative maintenance.
I brought it into the shop today to do a tranny fluid/filter change and my mechanic popped in a scanner to see what codes have come up in the system. Looks like code "201D-001" has come up with 47 frequencies. He believes it may be a clogging catalytic converter based on this code. Curious if anyone on here has experienced having this code and if swapping out a cat converter led to resolving rough idles?
I brought it into the shop today to do a tranny fluid/filter change and my mechanic popped in a scanner to see what codes have come up in the system. Looks like code "201D-001" has come up with 47 frequencies. He believes it may be a clogging catalytic converter based on this code. Curious if anyone on here has experienced having this code and if swapping out a cat converter led to resolving rough idles?
Try this:
