C230K Sport Coupe hard to start

[RajC230]

Hello,

I hope some of the Mercedes gurus can help.

I’ve had my 2002 C230 Kompressor Sport Coupe W203 (M111 engine?) for 5 years with no problems. Approximately 50k miles on the clock.

However, in the past month it has become difficult to start. Initially this was only occurring on cold starts but has now become a common issue.

Symptoms

• Car hard to start
• Engine cranks/rotates for 10+ seconds after turning key before engine starts/fires up.
• Sometimes will fail to start/fire on first attempt altogether, but does start/fire on second attempt.
• If I switch off the ignition and switch back on immediately for restart (or within a few minutes), engine cranks and fires up as normal. However, if left for 30 minutes or more and I attempt to restart – the above problems reoccur.
• On one occasion, once the engine had fired up, it felt as though not all of the cylinders had fired up properly as car was sluggish and was misfiring. However this cleared on a restart.
• Electrics/lights on dashboard come on as normal
• Engine warning lamp is on
• Car runs and drives fine when up and running.

What’s been done so far (in date order)

• Took to local mechanic
• OBDII scan threw up P0171 code (system too lean bank 1)
• Used Cataclean (exhaust cleaner) = no effect
• Changed cold start sensor = no effect
• Disconnected MAF sensor = no effect
• Changed MAF sensor = no effect
• (note MAF was fairly clean in the first instance – however some oily residue in the ducting after MAF)

• Took to Mercedes Birmingham Central for Diagnostic test - giving the following codes;
  • P201D-002 Self adaptation of mixture formation, the mixture is too lean in the part load range [P0171]
  • P201D-008 Self adaptation of mixture formation, the mixture is too lean at idle speed [P0171]
  • P2006-001 B2/5b1 (intake air temperature sensor) Signal, short circuit to positive / Open circuit in wiring [P0113]
  • P200B-002 B2/5 (Hot film mass air flow sensor), Short circuit to ground / Open circuit in wiring [P0102]

Verdict - Mercedes mechanic claimed that the above diagnostic codes were not directly attributable to the symptoms/problems identified and required further investigation involving stripping down parts of the engine to inspect wiring looms etc. For 2 hours labour just to investigate the problem I was quoted £288!!! I kindly declined.

Next steps
My local mechanic suggests it’ll be a trial and error process to get to the root cause – starting with checking wiring looms, replacing the basic sensors etc. Suggested I check the forums.

Similar forums suggest;
MAF
O2 senor fault
Oiled/dirty wiring looms/plugs
Fuel pump / Loss of fuel pressure / pressure regulator fault
Camshaft sensor fault
Possible air leak into intake manifold

Has anyone come across any similar problems and/or could offer any guidance please?

Any help would be greatly appreciated.

Thanks
Raj

 

[flango]

I would have gone for MAF first too, however this is very similar to what happened on SWMBO Audi and that was the O2 sensor however on the 230k the cam sensor magnet on the front of the engine gets contaminated with oil which gets into the wiring loom, the new sensor comes with plug to prevent this happening, apart from those 3 theres no other real common problems on the 230k

But you have MSL on your doorstep a very very good Indie contact ACID on here I'm sure they will pinpoint the cause of your problem very quickly