Rough idle on a Peugeot 406 HDI

My 406 hdi has a rough idle. When I rev it up it seems fine - a little misfiring, but soon it hits the turbo and it's OK. It feels almost like it's running on 3 cylinders on tick over.

A friend has done several tests, a flow test on injectors seemed fine, changed the fuel pressure sensor on rail and it's still no different. Has anyone suffered with these faults?

Asked on 1 January 2012 by scanny1

Answered by Honest John
Might be this: Mysterious 'Engine System Faults' on diesel leading them to lose power and revert to limp home mode may be caused by an intercooler pipe weld fault leading to a crack in the pipe. On 1.6TDCI the thin steel turbo to intercooler pipe can split. It cracks in two places in opposite directions emanating from the "start" and "stop" of the upper bracket weld. Fractures are of a fatigue nature resulting from vibration, the bracket being rigidly attached to the engine. By May 2010, turbo failures were becoming increasingly common on high mileage 1.6TDCIs.

Problem of 1.6 and 2.0 16v diesels slipping into limp home mode put down to throttle butterflies sticking or their spindles wearing prematurely causing them to stick. The throttle position sensor identifies this and sends a message to the ECU to limit the engine to limp home mode.
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