[artbuc]

I have attached a couple pics and a wiring diagram. I have a 99 Avalon XLS with a 3.0L V6 1MZ-FE engine. My problem is excessive initial fast idle speed at 2100 rpm. Toyota considers this to be in the normal range but I believe it is easier on me and the car to control initial fast idle to 1250-1500. Before making this repair, check your ECT sensor output to make sure it is working ok. Also, make sure all other idle speed controls are functioning normally, eg idle speed ramps up when engaging A/C and idle speed ramps down to 750 +/- as engine warms up to nomal operating temperature. Making this repair will "fool" the ECU into thinking the engine temperature at start-up is warmer than it really is. Once the engine temperature does warm up to normal, the amount of compensation automatically becomes insignificant. The effective resistance (RE) of two resistors in parallel (R1 and R2) is:

RE = R1 x R2 divided by R1 + R2

At 68 degrees, the ECT sensor resistance will be about 2.7 k ohms. If you add a 1.6k ohm resistor in parallel with the ECT sensor, the effective resistance seen by the ECU will be 1.0k ohms. Thus, the ECU will think the engine is 104 degrees and the initial fast idle will be correspondingly lower. In my case it dropped from 2100 to 1250 rpm. In the winter, you may have to slightly decrease the parallel resistor to maintain 1250. When the engine temp warms to normal, the ECT sensor resistance drops to 0.2 k ohms. The effective resistance is 0.18 k ohms which is well within the normal acccuracy of the ECT sensor output. So, the beauty of this solution is that you can set the variable resistor at whatever you need to to get the initial fast idle speed and that compensation automatically eliminates itself as the engine warms up.