Rpm surge.

[T-man]

New day new problem. Finally final fitted engine rigged up all belts hoses etc etc.
Here's my issue. My car has been off the road for 1-2 years and I fitted an engine from a car that has been off the road for 3-4 years. I've fitted new plugs new oil new oil filter new dizzy cap and rotor arm.
On start up it kicks in straight away but once warm it sits at the "normal" idle speed then 4 maybe 5 seconds later it goes up to say 1400 rpm then 3 sec later comes back down. I can physically see the throttle link the one at the throttle body move.
What's causing this?

Thanks in advance,
T

[popup]

Is the intake in good condition, any vacuum leaks?

Check the PCV valve is clear too.

Check the TPS setup, check the IAT and CLT.