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C320 runs smooth cold rough hot

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Old Feb 1, 2013 | 12:44 AM
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dfdfefjohnserrafdkefjef's Avatar
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C320 runs smooth cold rough hot

My 2003 C320 runs perfectly when cold, but when it warms up it starts to run rough, and will sometimes stall or almost stall at a stop. It has 115000 miles. I've changed the plugs. I figure it's got to be a sensor that kicks in after warm-up. Check engine light came on for a couple of days then went out. Haven't read the codes yet. Seems to run smooth at high speed (60-70mph). Any ideas?
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Old Feb 1, 2013 | 01:20 AM
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From: Toronto, Ontario, Canada, eh!
2003 C230 Sports Coupe, Paprika Metallic Red, Auto, Pano, Leather
OBD2 codes,...

Likely CPS,.... search!
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Old Feb 1, 2013 | 10:22 AM
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That's the Crank Position Sensor? It always starts. Can you tell me what code that is?
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Old Feb 1, 2013 | 10:48 AM
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From: Toronto, Ontario, Canada, eh!
2003 C230 Sports Coupe, Paprika Metallic Red, Auto, Pano, Leather
Lots of info on forum,.... search,... or just go to your local Mercedes-Benz Stealership and have them fix it,.....
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Old Feb 1, 2013 | 12:46 PM
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Ok, Thanks for the lead. I'm new to the forum, and didn't find much on my particular problem, Cold-smooth, Hot rough.
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Old Feb 1, 2013 | 03:40 PM
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From: So. Cal.
'02 C320 Wagon, '78 308 GTS, '06 Highlander Hybrid
Not a lot of info to go off of, but maybe check for a clogged catalyst.
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Old Feb 1, 2013 | 09:20 PM
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From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Please check for stored codes. It can be a whole host of things.

What symptoms tell me is that it is stable open loop with enriched mixture but rough in closed loop. Have you cleaned the MAF? Could even be dirty injectors or an 02 sensor.
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