Fast Idle 740 Estate

[noreply@invalid]

1988 740 2 Litre Estate

I have had an intermittent problem with the engine running fast at idle.
The revs at idle could be as high as 2700 level but mainly in the 1500 rev
range.
The problem seemed to have gone away for the past 6 months of its own accord
however as with most faults it has started up again.
What I have now noticed that the fault normally happens after a long run say
over 1 hours driving.
Any ideas what this problem is.

 

[Andy]

Probably an intermittent throttle position switch. Open the throttle
manually and you should hear a faint "click" right after opening. If not:
adjust/replace!

 

[Ricky Behrendt]

It could sound like a vacuum leak, check all hoses maybe one is cracked and
only leaks in certain positions.

RiBe

 

[Gavin Jones]

I have a 740 SE with the 2 litre B200E engine and am having real trouble
with a rough idle problem which has recently started.

The car when idling feels very lumpy and also semms very rich e.g. like it
is running on three cylinders. I have replaced the normal things e.g.

Air Filter,
Plugs,
Leads,
Distributor Cap,
Rotor Arm,
Checked for air leaks and so on ...

But the problem is still there, could anyone else shed some light on this ?

Engine runs fine otherwise, this is just on idle, not so bad when warm.

Regards,
Gavin Jones