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Idle air control valve bupasses IAT sensor

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I've got a celica ST205 which has the standard IAT sensor after the TB in the inlet manifold. The sensor is slow and heat soaks really bad and will pretty much just sit at 40 deg C so is pretty useless.

To fix that I installed one of the link/Bosch open element sensor just before the TB which works much better apart from at Idle with the TB closed the air for the engine is fed from a separate pipe from essentially where the air filter is and bypasses the charge pipework & IAT sensor completly. I've tried a couple of times to switch Charge Temp Correction on as it sounded like that was designed for exactly this problem but I couldn't get it to work at all so If someone else has had this issue how are you all getting around it?

I was thinking if i was to adjust the throttle plate at idle so it was slightly open and re tune my IACV settings would this work? My thinking is it would mean some air would always pass the sensor giving it a more acurate reading. Currently IASC duty cycle is around 40% at idle so there should be room for adjustment.

Thanks David

I think you'll find your issues are more related to not using charge temp estimate than the IAT sensor location itself. What we really want to know is the air temp of the charge air as it passes the valves and at low air speed this is predominantly a function of engine coolant temp more than air temp. There's a webinar covering this on the Link G4+ system that will probably be quite helpful - https://www.hpacademy.com/previous-webinars/075-charge-temperature-compensation-link-g4/

Hi Andre, thanks for the reply. I've been getting my head around CTE and it's starting to sink in be there was an issue with the throttle. On the UK 205 GT Fours (not sure if its just on the UK models) there's a little actuator which keeps the throttle open a crack until engine startup. Once vacuum is acting on this actuator it was essentially letting the throttle blade shut completely. This was causing the only path for the air at idle to go through the IAC valve. I've adjusted the throttle blade stop and adjusted the IAC duty cycle acordingly and it's working much better now. It's also addressed a dead spot in my TPS as the throttle plate was closing an extra 6% after the TPS was calibrated and the engine was running.

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