When i turn on my truck (while the engine is cold) my idle goes to around 1000 rpm. After I step on the gas for a little bit / drive it a little bit it goes up to the normal 1500 rpm for cold start. And after driving a little the 1500 drops down to closer to 1200 before the engine is warm.

I don't think its the IAC valve because I recently replaced that and before i replaced it, the truck would never idle at 1500 rpm. I have also checked the timing and the TPS which both seem to be fine. I have also replaced the ecu temp sensor and cold start injector switch. The throttle cable also doesn't have any slack.

I'm at a loss for what else it could be so any help would be appreciated

 

why replace the CSI switch? if the truck starts when cold, the switch is working properly. cold/fast idle speed has ZERO to do with the cold start system (csi switch, csi injector). also, the parts cannon method is expensive when trying to fix a problem (you've replaced the IAC, ecu temp sensor, and csi switch). if you don't have one, now would be a good time to obtain a factory service manual, which describes the testing routine for diagnosing issues in all the engine's systems. member @scope103 has a link to an online factory service manual, and has posted that link in numerous threads about engine/toyota diagnostics.

 

Yep i agree at a certain point i just starting throwing parts at it like an idiot. I definitely wasted some time and money there but it is what it is now. I'll check out a fsm