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This BMW E70 30D came in with a rough running idle. Our first step was to read fault codes, which indicated multiple glow plug codes, and next is to check for Carbon build up inside the inlet manifold. I removed the boost pipe off of the throttle valve and found heavy build up. The Inlet manifold was then removed from the vehicle and cleaned in a sonic bath, and the ports in the cylinder head cleaned via walnut blasting. This carbon build up can restrict air flow, interfering with the tumbling and swirl of the air, and cause cylinder imbalances due to varied air flow to each cylinder. This combined with glow plug activation codes on all 6 cylinders produces a rough, stumbling idle - especially in a cokd start scenario. The glow plug module was also replaced whilst the manifold was removed, after testing of all 6 glow plugs showed no problems. After repairs were carried out, the vehicle performs as it should and idles smoothly. The DPF back pressures were checked after repairs to ensure correct operation and no need for the customer to return in the near future.
