rough idel rev up and down

It may have a problem with the Idle Air Control (IAC) system. Could also be an air leak into the air intake system, look for loose or cracked rubber parts in the intake system. Here's a directory link for you: http://repairpal.com/toyota-repair-in-bowler-wisconsin

1. With the engine fully warmed up and the idle speed surging up and down, block the fast idle valve in the throttle body with a piece of duct tape and check to see if the idle speed goes to normal. 2. Check the coolant flow through the fast idle valve to make sure there are no restrictions. http://www.jaysauto.net if you need more help.

In the case of my 1992 Toyota pickup the "ghost revving" of the engine appeared at the same time I noticed that, although the vehicle was achieving normal operating temp, the heating system was sometimes delivering warm air to cab, sometimes not. I discovered my coolant level was down significantly. I filled the radiator back up and the "ghost revving" problem immediately disappeared. My guess is the low coolant level was somehow screwing with the mechanism that enriches the fuel/air mixture when the engine is cold and leans it out as the engine warms up.