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Jumping Idle

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Old 12-09-13, 02:54 PM
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smrtsmart
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Hi. I have a 1990 Lexus LS400. The check engine light was on and indicated a bad Idle Air Control Valve. I replaced the IACV and new hoses and when I went to start it up it idled really low and died.I tried getting the engine up to normal operating temperature by just feathering the gas and noticed a real jumpy idle. I also noticed a lot of smoke coming from the exhaust. Any idea on how to fix the idle? I also tried tightening the cable that makes it throttle higher but couldnt find the nut that is supposed to tighten it. Thank you in advance.
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Old 12-09-13, 03:06 PM
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Is there an adjustment on the IACV?
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Old 12-09-13, 03:37 PM
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Is there an adjustment on the IACV?
there is not! - it is completely control by the ECU



the Idle Air Control that you replaced it with, might be bad too, I would take it off and test it, as per the procedure here

the 3 throttle cables (throttle, transmission, and cruise control) should be adjusted to have slight slop/play, just a little bit, so not tight/taunt but not super loose either

if the IACV passes all tests, and you are sure it is all connected up right, then check for vacuum leaks etc. or a vacuum line not connected

if all that checked out, next step is too adjust the Throttle Position Sensor (TPS) as shown in the procedure here

if that is good, then you may have failing ECU capacitors

Last edited by LScowboyLS; 12-09-13 at 03:42 PM.
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