Excellent work on the Idle Air Control! I am certain we can figure this new problem out. We'll start with a couple of checks and questions to get started.
1) Does the overheating occur after 1 mile even when started cold? (Has sat for at least 3 hours)
2) Is the overheating symptom the gauge, and if so where is the needle rising to?
3) Is the overheating symptom steam from the engine?
4) What are the coolant levels for the radiator and overflow tank? FYI the overflow tank often looks as if it has fluid but is just a small bit that wouldn't drain. You can verify if fluid low in the radiator by filling and noting how much it needed. Add slowly and allow time for air to escape.
5) If the fluid is about 1 gallon low, pressure test the system with a pressure tester while the system is full and inspect under the hood and on the ground for the source of the leak.
Here is a site link for the basic coolant checking. http://www.2carpros.com/first_things/coolant_leaks.htm
I've probably overloaded you for now so, post back and we will proceed with the diagnosis.
Thursday, November 1st, 2018 AT 6:42 PM