Funny C 200 Idling Problem

Southafrica001
10

Asked by Jun 16, 2011 at 05:05 AM about the 2003 Mercedes-Benz C-Class

Question type: Maintenance & Repair

Hi
My C 200 petrol manual is a bit sick....Can someone help?
In neutral gear at a stop sign or when idling generally - The idle falls very low and a miss fire seems to develop. Funny part is that if you hold the throttle to above 700 odd revs, it does not do this. Worse still one it starts, you have to switch off the ignition and then restart and the problem goes away....it does not do this all teh time.....I have taken it into MBI agents who have replaced various components ( all vaccuum pipe, leads, plugs etc...spent about US 2000.00 already and no improvement.....what ever it is, it is small but MBI in South Africa are at a loss....latest suggestion is to recondition the entire head - Cost of about US 3000.00......and no guarantee that this will sort out.....Any suggestions?

Regards
C 200 Lover ( she is just a bit sick)
South Africa

8 Answers

Lorne Grandison
3,995

Check the coil packs, spark plugs, plug wires, mass air flow sensor. Once the car miss fires on a cylinder the computer will shut that cylinder down to prevent damage to it, subsequently the car will run horribly until you reset it. To reset it you'll have to switch the ignition off and restart. Check the ECU error codes using a OBD2 code reader to point you in the right direction of the problem. Sometimes a low idle can be caused by a filthy throttle body which clogs the idle air way causing the engine to die when you lift off the throttle. Also a bad engine wiring harness could be the culprit too. These cars are known for harnesses being broken down by high under bonnet heat that cause them to deteriorate causing intermittent problems with sensors shorting , etc. Reconditioning the entire head sounds like a rip off, they are grasping at straws. check the harness first.

1 out of 1 people think this is helpful.
Southafrica001
10

Thank you kind sir, I will pass your reccommendations onto MBI and lets see what they say this time... Most appreciated

1 out of 1 people think this is helpful.
disappointed_Merc_Owner
10

Hi I have the identical problem on a 2003 200k 1.8 C Class. I mean identical problem. From all the reading I have done this fault appears common and no one really knows what causes it. THe closest I have found is a guy that documented his same experience and sadly he did everything and the solution was to fit a reconditioned head. This cured the problem but it is clearly the last resort. I still need to check and clean MAF etc. What puzzles me isthat the problem comes on at tick over normally shortly after pulling up at lights. This makes me think the ECU is receiving inputs from sensors that make it cause the misfire. But why ? why shut down fuel to a cylinder. I tested the compression on my engine and found n1 cyclinder down by 40psi compared to others. The problem when it happens is either 1 or 4. I have changed coil packs and problem still present. The one thing this has confirmed for me is that the build quality of german cars being good is a myth. I have owned BMW, Merc, Porsche's now and have to say that they are extremely poor when compared against other lesser brands. I have had some japanese cars that are bullet proof running them for years and changing nothing. This is my last time I buy German car as my experiences have been they are expensive rubbish. Good luck if you find a solution please update on what you find. Thanks

disappointed_Merc_Owner
10

PS sorry forgot to say that the Cylinder head issue is apparently a known defect on this engine. The fact MB are indicating it as problem make me suspect they know but that is not to say other factors are not causing problem so don't rush to change head. Check the cheap and obvious first. But don't be surprised if you end up at the head....... I hope not.

David Larkin
0

Iff you read the haynes manual ..it points to refilling the coolant bottel ss the incorect coolant causes fluid loss....with my c class. It devoleped a tiny leak into piston no 1...same misfireing at low reves but clears as you drive only to return again at low reves.. everything was triple checked and is all good ...leaking cylinder head gasket.... replacing cylinder head ect...best price in Ireland is €1000:00 euro..might get someone to get it done a little cheaper...not happy man

David Larkin
0

Ok...its not rocket science. .iff a coolant bottle erupts a fountain of bubling water...its head gasket gone/waterpump.....with this mercedes eratic problem....yes coilpacks can breakdown....but think ...with a tiny ,stream of presurised water at low tickover entering one or two cylinders ...to then have the increase in pressure in the compression with increas in reves equalise against the coolant system pessure ...hence the " car runs fine in higher revs ..its only on tick over it missfires ( moisture on plug) happens ...very difficult to spot ss residiul heatin the block leaves the plug tip dry up ..I

disappointed_Merc_Owner
10

Thanks for thoughts. In the end it was confirmed as burnt exhaust valve(s) when head was changed and great expense. It was the problem that Mercedes knew about but kept quite on until the vehicle was out of the period they would repair free of charge. This was my one and only Merc. People who had had Merc's warned before I bought it that I would regret it and I did. An expensive mistake. For Mercedes the so called experts in quality and reliable car building this car was junk. With really poor aftercare. If your issue was something else I am pleased as maybe it was not expensive as mine. Always start with the basics and cheap parts to change and hope that cures it. I find some good references on line from others who suffered the same problem. The acid test is a compression test. It was obvious which cylinder was low on pressure. When fixed car went ok but I had lost faith it it and have now sold it. I would never touch another Merc again.

1 out of 1 people think this is helpful.
janstew
20

Oh God, just had my plugs changed on my C 200 1998 and I'm getting the idling misfire spoken of above. Mechanic already changed the plugs out and no doubt will now check the leads, coils, etc etc

2 out of 2 people think this is helpful.

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