Release the Cancel button once the LED lights come on. This resets both the printer and the NVRAM together. Press and hold the Reset button near the back of a 5P or 6P printer as you turn on the power. Holding it for less than 20 seconds resets the printer only.
Once the throttle body is exposed, spray the throttle-body cleaner inside the air duct, and use the brushes to gently dislodge the dirt, gum and varnish that are present. Note: Be very careful not to let the thin, plastic spray nozzle (or anything else!) fall into the throttle-body opening.
If it does, you have a vacuum leak. After checking if you do not find anything, at least spray some throttle body cleaner in the throttle body and clean the throttle blade up. Also try the Idle air Control Valve Located on top of your throttle body, or even the throttle position sensor.