The idle on my ST165 has been gradually getting lower and lower. It's hovering at about 500 RPM right now. I checked the timing and it's ok, inspected the plugs, replaced the cap and rotor but it's still idling low. I found a small leak in the exhaust and sealed that up but it's still at 500 RPM. Since it's been gradually getting lower and rougher, I suspect it may be another exhaust leak that I can;t see. Gonna go by a shop and see if they can find anything... Getting a bit frustrated, any ideas? Am I missing something simple?
It can be that you have something draining the battery, so your generator have to do extra work, but the ECU doesn't know about it and does not raise idle to compensate. You can try turning the lights on while engine is at idle and see if anything changes (that's a drain that ECU is aware of, and should adjust idle).
So I ended up re-setting the ignition timing 10 BTDC and then adjusted the idle screw on the throttle body. Runs at 750 rpm now and has smoothened out. Odd that the BGB has absolutely no reference to that idle screw for the 3SGTE motor (!). Anyways, gonna monitor it and see if it changes or not. I suspect that i may have an exhaust or TB gasket leak(?)that I can't see. I do plan to clean the TB like you suggested. Thanks for the input, gentlemen!
