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Thread: AC Idle up issue - 1NZ-FE

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    Default AC Idle up issue - 1NZ-FE

    Assalamulaikum all.
    I need some help with an issue that I've been facing for some time now. The car in question is an 03 Corolla that has a 1nz-fe swapped into it. Now the issue is that with the AC turned on, the idle speed does not increase as it should. Neither does it increase when the steering wheel has been turned to maximum or when depressing the brake pedal at idle. I've tried 3 different throttle bodies with the same results.

    However, at cold start, the idle goes up perfectly the way it should. I've taken apart an idle control valve from one of the throttle bodies and connected it stand alone with the icav connector to see if it moves with the ac on, it doesnt.

    I've checked the continuity at all three wires of the connector and its fine. The middle one gets +B, the left one ground, and the right one signal from the ecu.

    I've got a 2nz-fe in my charade and I've compared the voltages with it. At idle, it has the same voltages as the 1nz but when the brake pedal is pressed or the steering is turned to the maximum, the voltage on the third pin in the icav connector (the one controlled by the ecu) drops from around 6.9v to 6.2v and the idle goes up the way it should whereas, in the corolla, it stays at 6.7v without an increase in the idle.

    I'm attaching a couple of videos to show you what I mean. The first one is of the charade and the second one of the corolla. The second video will also show the difference with the AC running towards the end.

    Any insight on this issue would be highly appreciated. Thanks.
    @Xulfiqar and @SER_GTR Please help me out here. Thanks.





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    NiGhTShAdE's Avatar
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    Default

    Yeah i meant maf ....wrongly written map....
    btw it should have been asked before anything....What are the rpms on a/c when idling?

    Sent from LG Optimus LTE LU-6200 using PW forums mobile app
    NiGhT ShAdE>>~

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    Default

    Currently, I have the rpm adjusted manually at 1k without ac so that it stays at around 750-800 when the ac is turned on. If I keep the idle at 900, with the ac on, it goes to around 650-700 at which, the idle becomes a little jittery.

    Sent from my HTC One S using PW Forums mobile app

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    Default

    If Nothing Works...Try That Valve ....It May Resolve Your Issue W.o Bashing Much Of Your Head ....! Its Very Popular Among Mechanics
    TOYOTA Sprinter 86- AE80 DOHC 20v'D TOYOTA Corolla 98- AE101 4AFE 16v

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    Default

    do resistance check on your IACV solenoid and check if its clogged. If there is no change on idle this can mean few things

    1. Your ECU is not controling it
    2. Your ECU says it to control but it does not control by adjusting valve
    3. it adjusts the valve but no effect on rpm

    if nothing works i would do one thing i would remove the compressor relay and then turn on the ac. if idle rises i would know it is working saying it because may be compressor is kicking in and taking a bit load so instead of increasing it decreases. but i doubt that. make sure your ecu is wired properly. how do you know that compressor is controlled by ecu? did you checked the wire
    93 Accord CB7 (Sold) / 2005 CL7

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    Default

    The ecu is controlling the ac, I know this because most of the wiring is stock and like I said earlier, it has not been touched by local ustaads and any changes required in the wiring for the swap were done by me and no corners have been cut.
    I've removed the ac relay to check if its increasing idle, it does not and it wouldnt because its designed in a way that as soon as it detects any load, then only it increases idle. Without the compressor working, there's no load on the engine.

    The iacv, like i mentioned earlier is fluidy smooth and its not clogged at all. The idle increases at cold start and then comes back to normal once the engine is at operating temperature, which shows that the iacv is working fine.

    Now the issue is, either the ecu is not registering load for some reason or its trying to increase idle but is not able to for some reason.

    Sent from my HTC One S using PW Forums mobile app

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    Default

    I've found a solution for the problem. The idle control valve like I said earlier, has 3 wires, one is +12v, the other ground and the third one is the signal wire from the ecu. With the ac running, the signal wire should get a little under -6v for the idle to increase which for some reason was not being given to it by the ecu while the ac is running (it was getting around 6.8v from the ecu) though its functioning totally fine with cold idle. So I made a small circuit that gives it around -5.8v when the ac turns on and bypasses the signal coming from the ecu while the ac stays on. With that, the issue has been resolved and running fine now alhamdulillah.

    Sent from my HTC One S using PW Forums mobile app

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    Default

    @Owais_Yunus

    What (which device) is the source of the negative power supply rail? Is it the ECU?

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    Default

    check for air leakage, An idle not getting adjusted can be due to air leakage from the intake manifold.
    Also check the throttle shutter for any leakages, Is it allowing air to pass through IACV at close position.
    AE 86

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