YotaTech Forums - High idle switch anyone ?

Recently I was sitting for a while with the inverter running several lights and noticed the battery voltage was going down. If I reved the engine up to around 1200-1300rpm the alternator would put out almost full output and keep up with the load.

So this gave me an idea, why not put a high idle switch on the 4runner.

Most all of the public service vehicles have them so they can idle the engine up for better engine cooling, more alternator output, and much better cooling from the A/C. So after reading the FSM for a bit I realized if I could trick to engine to think its not fully warmed up (but not cold) I could make it idle up.

So I cut the wire to the engine temp sensor and put a 10K variable resistor in line with the temp sensor. I then plugged in the ODB-II scanner and once the engine was fully warm I started to turn up the resitor and watching the engine temp on the scanner. As I turned up the resistance the engine idled up to around 1300 rpm, with the computer thinking that the engine was around 135 deg. Any lower than 120-125 F the engine will go into open loop and use more fuel.

But as long as you make the computer thing its over 125F it will go into closed loop and not adjust the fuel trim, all it will do is just idle the engine faster. After I found the setting on the resistor to equal 135 F I took it out, measured it and put a normal resistor with a switch that will put it in line.

So now if I want to sit with the inverter on, make the A/C keep me cool or run the winch, I flip the switch and it idles up to 1300 and stays there all day long.