I have a Escort Cos Big Turbo model

The problem is:
When cold the idle ticks over at approx 1000 rpm after the cold start cuts out

But after 20-30mins of driving the revs go upto 1400-1500 rpm
while idling at traffic lights etc.

Can anyone guide me the right way of fixing this?
as i cant drive it around like that,as it cant be doing much good

Thanks in advance

Chris.

 

intake manifold gasket ?
apparently the standard originals are poo
my small turbo did exactly the same
& decent garage near me sorted it!
result - smoooooth idle

 

Cheers i will try that,

Anything else maybe
Off to Fords again tomorrow with a little list of bits

Chris.