I have no heat when idiling could it be a air lock

This sounds like a restricted heatercore, remove the two hoses to heatercore, take a waterhose and blow water through the heater core connections to clear out the core, i use two peices of heater hose, i slde them onto heatercore where the hoses were removed then put the hose nozzle against one end of the hose and blast water into core and see what comes out the other end then do the same on the otherside, this is to me done a few times until clean water flows out and i will bet it will solve the heat problem, because at idle theres not enough force for the coolant to flow through the core and when you rev the engine it forces coolant through the restricted core, hope this helps, good luck.