Originally Posted by arididit
The old mans just bought a 2003 Focus TDCI 115ps Ghia and when it starts it makes a rattle type noise. Not sure what it is. ... The only problem is this weird noise when starting up. ......It always starts just with a little knocky type noise.
Any ideas?? Should he take it back and get his money back?
This is the dual mass flywheel (DMF) going through resonance as the engine accelerates throught the critical resonance speed. It can get worse with age as the DMF gets 'slacker' and clatters from stop to stop more as the engine runs up to idle.
There's not much you can do other than buy a new DMF and have it fitted... or live with it!
There may be a calibration upgrade for the ECU from Ford to help accelerate the engine through this speed quicker, reducing the rattle? Checking the TSB's will show if its available.
The engine may sometimes crank, then fire and REALLY rattle like its going to shake itself apart. Mine does this perhaps 1 start in 100. This is when the DMF goes into resonance but there hasn't been enough acceleration for the engine to ge tout of the resonance band, so it remains stuck at the resonant frequency (450rpm IIRC).
If it does this switch it off immediately as the DMF can rattle itself to pieces.
Hope this helps? Steve