Date registered: Oct 2010
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E500 - Rough running when cold / P0410 CEL
I am looking for some ideas to troubleshoot my 2004 E500. It has 73k on the clock and has been well maintained and always fed premium fuel and Mobil 1 0W40 at regular intervals.
About 2 weeks ago it began running a bit rough for the first mile or two when cold. No DTCs present when scanned, so I checked the Ignition packs / leads / plugs. Nothing obvious but the plugs looked a bit tired - made a note to change them when I got a spare weekend.
Last week I was greeted by a lovely 'Check Engine' light. Scanning showed a P0410 - Secondary Air System problem. I checked the pump was working correctly and pushing air when it should - all fine. Checked all the vacuum hoses - look fine. So, out with the valves - Lots of carbon build up. Cleaned them up and checked the diaphrams were working and dropped them back in.
Also changed the plugs, new Bosch Platinums OEM type, cleaned the ignition cables e.t.c also completed an oil change (Mobil 1 0W40 of course!). Finally, reset the P0410 code.
500 miles later, the P0410 code is gone, all codes are clear BUT the rough running is still present when cold, perhaps slightly worse and also the engine now runs rough for 1 to 2 seconds when coming to a halt after a long drive at moderate speed. Other than that, the car drives great, normal power and smooth as ever.
So No codes showing, but still not right!! Before i commit to a large hit to the wallet and take the car to the stealer, any of you gurus got any top tips on what to check next ?