Mercedes Benz S320 W220 Petrol - 2001 - 97,000ms - rough idle

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Thu 25 Nov 2010 15:31
Mercedes Benz S320 W220 Petrol - 2001 - 97,000ms - rough idle - johnnieG

Hi All !

My MB s320 petrol with good MB service history has developed a rough and lumpy idle, dash temp gauge is slightly higher, MPG decreased, dash showing no malfunctions, slight hesitation from rest when cold or hot.

Has had the secondary CATs replaced with high quality stainless steel metallic ones due to the MB developing a nasty rattle. the rough idle was with the vehicle b4 and after the CATs were changed about 4 weeks ago.

Got it booked in with the local MB s****** (dealer) next week for diagnostic check-over.

Can anybody help?

J (new member today)

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Thu 25 Nov 2010 18:18
Mercedes Benz S320 W220 Petrol - 2001 - 97,000ms - rough idle - elekie&a/c doctor

These V6 engines are generally fairly reliable on the engine management system.However there are a few issues that could cause this problem.Check spak plugs and leads.There are 12 on this engine.Also check condition of the rubber o ring seal where the air mass meter clips into the inlet manifold.These become hard and don't seal properly and thus unmetered air enters engine.hth

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Fri 26 Nov 2010 14:28
Mercedes Benz S320 W220 Petrol - 2001 - 97,000ms - rough idle - johnnieG

Thank you for the good advice I will tell the merc dealer next week.

Kind regards, J

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