205 "Drives" Itself...

[brumbrumjo]

This is going to seem a very basic question to all you techies...

Anyway, here goes (least I can drive proper, no dents on this one).

My lil' ol' 205 (diesel) has taken to revving at an enormous rate, whilst it should be idling in town (many glares in town from zebra-crossing-users), and will quite happily drive itself along at 60mph along country roads when it should be doing 30mph (with a little steering help from moi).

In the past it has occasionally done this, to a minor degree, only noticeable on quiet country lane corners (thankfully).

It's getting a little dangerous.

Is it a big (ie expensive) problem, or is it something to do with the fast idle control? Is this easy and safe to do oneself? Are garages wise to this or are they gonna try to rip me off (should i go in disguised as a bloke?) like so many times before?

[Donaldiesel]

Hi Brumbrumjo,
There is a fast idle contol which is screwed into the thermostat housing. It has a steel cable to the injection pump. When the coolant heats up the cable should relax and reduce the idle speed. However, the control often seizes up with corrosion and so idling is too fast once the engine warms up. Simple job to replace. Part costs about £18. You will loose some coolant and need to top up antifreeze after. Find someone who knows the proper air bleeding procedure when refilling the coolant. Diesel engine can be damaged if air bubbles remain in.

However, if the revving is really as high as you indicate, it could be a stuck or frayed accelerator cable (approx £20) or a faulty injection pump (£megga). I suggest check the cables first, then if not cured see a fuel injection specialist. It will be useful for you to know if you have a Bosch or a Lucas injection pump.

[504gld]

Also check for air leaks in the fuel system, this will cause self accelleration for short blasts! Check the unions around the fuel filter, pump etc.