Idle surge

Hi folks I’m after some advice. I have a 1.8VVC fitted with a 48mm alloy TB & aftermarket air filter. I have recently done a full service, fuel filter & cambelt change. Car starts fine, warms up correctly & drives good, problem I have is at idle after warm up I get a surge now & again up to about 2K & if left longer the idle becomes rough & stalls. I have another VVC & have swapped the IACV & reset it & also the TPS & it’s still the same. Any advice would be welcome, thanks. 

When that happens have you tried to disconnect both hydraulic control valves - solenoids and see if that will resolve the problem? If it does you have 2 solenoids which needs replacement.

I’ll give that a try, thanks.

Well I tried it but it was the same, however whilst rooting around I found that my air temperature sensor was unplugged from the inlet manifold & someone before me shorted the plug terminals together, no idea why. Anyway I have plugged it back in & it’s running okay now.