CORRECTED LOW IDLE
I decided to get after this. My reading of the Toyota Big Green Book said that when idle is not at spec, the Idle Speed Control Valve might be to blame. In the instructions, it said initial conditions ought to be: Engine at normal operating temperature, and idle speed set correctly.
I had the sense that there must be an idle adjustment screw somewhere, but where? I texted my Toyota tech friend, and asked him. He called me and walked me through how I ought to proceed. He said that I should first thoroughly check for vacuum leaks by spraying carb cleaner or throttle body cleaner on all of the hoses from the air intake past the turbo and intercooler, to the throttle body. If there's a leak, then that should be addressed rather than adjusting the idle set screw.
Then, I sent him a photo of the throttle body. I could see a screw there toward the front of the car, right above the hose from the intercooler into the throttle body. Left is more open, and therefore higher idle, and right is tighter, for lower idle.
I gave the vacuum lines a good spraying down with throttle body cleaner. Note to self: Throttle body cleaner is nasty stuff…don’t inhale even a whiff. Best to just hold your breath while using it or exhale slightly to create an overpressure. The engine did not have any vacuum leaks.
I then turned the idle control screw one and a quarter turns to the left, and the idle settled in at 800rpm. Perfect! Problem solved. I’d read a number of posts and articles on low idle, and there was a variety of possibilities. Nice to know that the 3S-GTE--at least the Gen2 I don't know about the newer gen motors!--is a sufficiently old school motor to have a physical idle control adjustment.
I decided to get after this. My reading of the Toyota Big Green Book said that when idle is not at spec, the Idle Speed Control Valve might be to blame. In the instructions, it said initial conditions ought to be: Engine at normal operating temperature, and idle speed set correctly.
I had the sense that there must be an idle adjustment screw somewhere, but where? I texted my Toyota tech friend, and asked him. He called me and walked me through how I ought to proceed. He said that I should first thoroughly check for vacuum leaks by spraying carb cleaner or throttle body cleaner on all of the hoses from the air intake past the turbo and intercooler, to the throttle body. If there's a leak, then that should be addressed rather than adjusting the idle set screw.
Then, I sent him a photo of the throttle body. I could see a screw there toward the front of the car, right above the hose from the intercooler into the throttle body. Left is more open, and therefore higher idle, and right is tighter, for lower idle.
I gave the vacuum lines a good spraying down with throttle body cleaner. Note to self: Throttle body cleaner is nasty stuff…don’t inhale even a whiff. Best to just hold your breath while using it or exhale slightly to create an overpressure. The engine did not have any vacuum leaks.
I then turned the idle control screw one and a quarter turns to the left, and the idle settled in at 800rpm. Perfect! Problem solved. I’d read a number of posts and articles on low idle, and there was a variety of possibilities. Nice to know that the 3S-GTE--at least the Gen2 I don't know about the newer gen motors!--is a sufficiently old school motor to have a physical idle control adjustment.