Kitchenaid oven KGRT607 HBS6

350 will be the design max for your oven unless the handbook says for your model is higher rated and is faulty
repair or replace with a higher rated temp oven

Good Morning Friend,

I understand that your Frigidaire oven will not heat to temperature if you set it to 350 degrees. I see that you have to set it to 450 degrees for it to heat up, and then turn it back down to the desired temperature. Please try resetting your appliance, by either unplugging it or shutting the power off at your home's circuit breaker, for 3-5 minutes. Restore power, set the clock and try setting the temperature to 350 degrees. I ask that you please follow up with a comment on the post, at your convenience, to advise if further troubleshooting is needed or if your appliances status has changed successfully. Hope this is helpful.

-Best Regards-
WP

Generally the oven temperature will fluctuate as much as 30 degrees above or below the set temperature. The longer the oven is on, the less the temperature fluctuates. If you measure the highest and lowest temperatures readings with a thermometer after the oven has been preheated at least 20 minutes, you should come up with an average temperature somewhere within about 10 degrees of the set temperature. You can calibrate most ovens up to 35 degrees higher or lower if it is off. Any more than that requires replacing parts.

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It is normal for the thermal device to turn on and off. Obtaining a steady temp is not always possible. When setting a temperature on some ovens, they have what is called a tolerance point. That means a set temperature has a range of a few degrees up or down. At the Down point, the oven is triggered to energize the coils and bring the interior of the oven back to the settings desired. The other factor is opening the oven and allowing cool air to enter, or in some cases a leaking door seal allows air to enter and heat to escape.

replace the oven safety sensor located in the upper left corner of the oven cavity,its merely a thermocouple and cycles the temp in the oven and is easily replaceable,its a whirlpool part # AP3083985 available from most appliance parts stores that handle whirlpool parts,as this unit is produced by whirlpool corp. for kitchenaid corp.

This sounds like a weak igniter, it would have to be a gas oven and the symptoms usually are: takes longer than normal to ignite the burner, may or may not smell gas in the oven, does not maintain set temperature or burner does not come on fully, eventually won't heat at all. On gas ovens, a glo igniter is like a light bulb, the more you cook, the faster it wears out. Bottom line, needs to be replaced. Good luck. 

From the symptons you describe, I would say that the oven thermostat is faulty, and in need of replacement.
Make sure your thermometer is o/k by checking it against another one, or boil some water, and check the temp of the boiling water, this should determine if your thermometer is o/k.
Hope this helps.

Oven temp sensor failure, possible control board problem. Unit thinks its a different temp. sensor connects directly to control....suggest you to call maytag cust service....sometimes they will assist with parts

Always preheat your oven and let it cycle at least 2 times. Your unit may show 350 but the manufactures know that it is not 350. When it registers preheated, it really means that it is at an acceptable temperature to start cooking. If you think that it may not be calibrated correctly, your owner's manual will have instructions on how to recalibrate your oven. You will be able to raise or lower the temperature by + 25 degrees or - 25 degrees. As far as the gas smell, you will from time to time smell a gas smell with a gas oven especially if you are right at it when it ignites. If you are smelling gas when it is not in use then you should be extremely concerned.

I have the exact problem. We had the ignitor replaced 2 already and it works for 18 months and stops. Occasionally, it the oven won't even start to heat. I am ready to throw it out.