losing idle when hot
09-12-2009, 05:18 PM
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losing idle when hot
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?
09-12-2009, 06:01 PM
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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.
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.
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09-13-2009, 01:03 AM
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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?
Jay351: What's your plan for a fix, just replace that wire?
Last edited by woodendude; 09-13-2009 at 01:05 AM.
09-13-2009, 06:14 AM
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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
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 tempuraturethat's why idle and timing are to be set once the motor is fully warmed up
09-13-2009, 10:37 AM
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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
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 tempuraturethat's why idle and timing are to be set once the motor is fully warmed up
Last edited by woodendude; 09-13-2009 at 10:39 AM.
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