cjones1980@blueyonder.co.uk schrieb:

Perhaps a defunct sensor. If there is no check engine warning light you
have to run an engine check program in order to locate the problem.
Idling is regulated by the rather complex motor and catalytic converter
management.

Two possibilities come to mind:

A vacuum leak between the mass air sensor (MAS) and the intake manifold
or a split vacuum hose that's attached (or should be) to the intake
manifold. As the motor slows a small vacuum leak becomes proportionately
greater to the air moving into the motor. Unmetered (leaking) air
dilutes the air / fuel ratio so the motor will be underfueled and stumble.
Idle the hot engine and listen for a hissing sound that indicates a
vacuum leak. Check the clamp connections to the MAS and those rubber
boots, also check the air duct's clamp to the intake manifold.

The second is the fuel pressure regulator, a small drum attached to the
fuel rail to which the fuel injectors are attached. The regulator has a
vacuum hose attached to it (hose's other end is attached to intake
manifold). With engine OFF simply remove the rubber vacuum hose from the
regulator; the regulator is defective if fuel drips from it.