It is difficult to troubleshoot potential causes of temperature swings via comments, but some causes for temperature swings could be: - Quality/Type of Pellets - Opening the lid too often during cooking - Issues with combustion fan or sensor - Weather conditions Please note controller tolerance +/- 20°F is normal. To achieve the lowest temperatures (160F - 225F) on Member's Mark Pro-Series Pellet Grill, you will need to use the "SMOKE" setting. While in the "SMOKE" setting, you will not be preheating to a set temperature. Instead, you will use the "P" button to adjust the delivery speed of the pellets to the firepot, until the correct temperature is achieved on the digital controller. Allow 5-10 minutes for temperature to adjust, before changing to a different "P"setting. Flipping too quickly between"P" settings could cause dramatic temperature swings. For video instructions and tips regarding your Member's Mark Pro-Series Pellet Grill, please visit our YouTube channel. You will find videos on such topics as: - First use set-up - Setting temperature - Using the "P" setting and more! https://www.youtube.com/channel/UC7QXVGnKvDqwuL5GtCg1h5g/videos Should you require further assistance, don't hesitate to reach out to Member Support at (888) 301-0332 from 7 a.m. to 11 p.m. CST Monday through Saturday and 10 a.m. to 8 p.m. CST on Sundays. Please have the item number from your receipt, the serial number, the product UPC and/or the product description ready to provide to our Member Care Professional.