Normally if the oven is not getting to temperature it would be down to one of the following
· Thermostat – Gas valve
· Thermostat bulb location – The copper bulb that sits in the oven on the side wall, if this falls or is not in place then the oven wont regulate
· Oven door seal, if the seal is damaged then the heat is escaping to quickly from the appliance
· Cavity damage, again if the oven cavity is damaged or not assembled correctly then the heat will escape to quickly and prevent the appliance getting to temperature
· Insufficient/poorly placed insulation – If the insulation is damaged or missing this will again mean the heat escapes to quickly
The jet wouldn’t normally effect the temperature that much, if the jet was wrong or blocked and therefore not allowing enough gas through we would expect to see a poor flame or yellow flame as well.