91 auto, 4 runner, 403,500kil. In the last little while I'm losing my idle when the engine is hot ( hour or so of driving) it isn't constant though. I can be sitting at a light and it'll drop to 300-400 rpm and 2 lights down the road it'll idle at 700-800 rpm. I've changed out the plugs and wires, rotor and dist. cap Also about the same time has gotten hard to start hot, it'll crank a few times before it goes.alweays started first crank hot or cold.... Any ideas?

 

mine does the same thing. I have a bad TPS wire to the ecu, Im pretty sure thats it..

 

vacuum leaks?

 

IACV maybe? but I think that would be more of a high-idle problem... I dunno though, it's possible

 

If the IACV is stuck in the 'hot'/closed position, the truck would have issues cold starting- idle too low.
If the IACV is stuck in the 'cold'/open or somewhere in between, then that may be an issue: if the IACV is stuck partially open, or won't fully close, then the air bypassing the throttle will be more than the ECU expects based on the coolant temp sensor input and could cause a lean condition but the AFM should signal an increased air flow and that should just make it idle higher.

Well, ... unless it was tuned to the stock idle and timing with a stuck IACV and the engine was cold.

Did that make sense?

My head explodes.

 

ITs called the wax valve on the 3vze btw

 

yeah you just confused the hell outta me...

lol

 

Abe: If the case was vacuum leaks wouldn't it be a constant? and what is this IACV that you speak of? Where is it located, do you have a picture of it?
Jay351: What's your plan for a fix, just replace that wire?

 

IACV = Idle Air Control Valve

regulates and bumps up the idle at cold start

uses the heat from the coolant to open up once the motor warms up, and then the valve opens (or closes, however it works ) and then drops the idle to normal once warmed up to operating tempurature

that's why idle and timing are to be set once the motor is fully warmed up

 

I've done a fair bit of reading since I asked that question and I'm thinking it may not be my problem, she starts fine cold and idles high as it should. I did however find my MAF ( i think that's what it's called, top of airbox) connection not snapprd in on one side and quite loose. I snapped it back into place and seems to be good so far, but haven't driven it enough to say for sure. I'm also beginging to think that maybe snorkeling into cab may be part of my problem. Could it be I'm not always getting enough air or to warm of air?