hi, i own a 3dr cossie, its got a PJ stage 3 conversion and is now running a 4x4 escort cosworth engine.

now i have a problem with the idle speed, it wont go lower than 1200 rpm, the base idle has been set up and when the plug is put back on the engine revs then settles at 1200 rpm.
the idle valve has been swapped for another yet still happens.
is there a sensor that controls this or what else could it be?

cheers