My truck keeps surging. Up and down. The idle is always different. No check engine light. I burped the system. My truck over heats (new thermostat) and the idle screw is just about all the way down. So, what do I do? Can a coolant temp sensor cause this? Thanks

 

Radiator cap/fan clutch/radiator

Replace these parts individually in that order until your overheating problem goes away.

Overheating on the freeway (high speed driving) usually indicates a plugged radiator. Low speed overheating usually indicates a bad fan clutch.

 

I'd start with a coolant temp sensor, chances are its not actually overheating, just the gauge reading incorrectly. Would explain the weird idle too.

 

before you spend money try this as it was a fix for mine (same symptoms you have).... i took the small coolant hose off the throttle body nd blew it out with my air hose and all is well....a toyota tech said tey do this for a fix as well. i fixed mine back in the summer and all is well

 

Thanks guys. I was also thinking on the lines of a coolant temp sensor. My dad had one go bad on his ford and it overheated, we parked and opened up the hood and it wasn't hot. So, I really don't think it is overheating...I think it is trying to trick me. Thanks, I'll report back!