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warm idle issue

This is a discussion on warm idle issue within the Computer & Tuning forums, part of the LSx Technical Help Section category; Once the car gets into closed loop the idle gets rough. Also when I come to a stoplight the car ...

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    warm idle issue

    Once the car gets into closed loop the idle gets rough. Also when I come to a stoplight the car will start to idle slightly low for maybe 5secs then rev back up to normal. In this low idle state the 02 sensors reading all drop to single digits. I have 0 codes and so far have tried another maf, vacuum leak lests, new coolant temp sensor and still have the issue. I'm thinking a slow 02 sensor but I don't think all the 02 readings would drop at the same time. I read live data with just predator. I have tested the throttle position sensor and it checked out fine. Maybe the 160 thermostat or the iat possible? Help me please.

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    Member fast enough Z28's Avatar
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    98 camaro z28 m6

    Either the IAC or IAT sensor would be my guess

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    I've tried another iat sensor that I have on a stock lid and no difference. I have cleaned the iac many times with throttlebody cleaner to clean the carbon buildup. Is there a way to test it, the iac?

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    Veteran 0rion's Avatar
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    what do your fuel trims look like? What % are they? Any work on the car lately up around the intake area?

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    Quote Originally Posted by 0rion View Post
    what do your fuel trims look like? What % are they? Any work on the car lately up around the intake area?
    No work around the intake. I have a vacuum gauge inside the car and it doesn't flunctuate. My fuel trims are around negative 3-4 driving and little lower at idle. I've had this issue for about a yr now.

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    Senior Member mrr23's Avatar
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    Quote Originally Posted by occamaroz View Post
    Once the car gets into closed loop the idle gets rough. Also when I come to a stoplight the car will start to idle slightly low for maybe 5secs then rev back up to normal. In this low idle state the 02 sensors reading all drop to single digits. I have 0 codes and so far have tried another maf, vacuum leak lests, new coolant temp sensor and still have the issue. I'm thinking a slow 02 sensor but I don't think all the 02 readings would drop at the same time. I read live data with just predator. I have tested the throttle position sensor and it checked out fine. Maybe the 160 thermostat or the iat possible? Help me please.
    what mods done to the motor? stock cam? stock heads?

    this is just a guess:
    sounds like Deceleration Fuel Cut Off is staying on too long. also, in looking at the DFCO table, if the TPS reads under 1% at 800 rpms, it keeps the injectors shut off. then, once the engine hits the 400 rpms, it'll shut off the DFCO.

    unfortunately, you cannot make any changes to the DFCO tables with the predator.

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    Veteran 0rion's Avatar
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    also just out of curiosity have you tried removing the predator tune and running your stock tune to see if it still does it?

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    Senior Member mrr23's Avatar
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    dark bowling green
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    just remembered another reason for this. the rich/lean switch points might be causing this issue as well. look in the mrr23, hptuners part 2 thread for that explanation. again, with the predator, you can't change those points though.

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    Quote Originally Posted by 0rion View Post
    also just out of curiosity have you tried removing the predator tune and running your stock tune to see if it still does it?
    Stock tune is in the car now. Weird thing is the car never did this before until about 1yr ago. I guess I will just have to live with it since it isn't effecting driveabilty or power.

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    Senior Member Justin23454's Avatar
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    what should you idle at? I idle around 5-800 rpm? 500/600 in P 7/800 in N

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    no reason to live with this. There's a reason somewhere. List all of your mods for us to give an idea of how modded the car is. Sounds like issues a cammed car would have. Usually an airflow issue.

    edit
    I just looked at your profile, are those mods current? Are you still running the maft?

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    Mods are just a lid. maft, and powerstick muffler in the midpipe. I have tried disconnecting the maft and it still does it.

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    If you're running the predator I would take the maft off and leave it off. No reason for it since you have a predator. After you tried it without the maft did you give it a little drive time to let the car relearn trims? ~50minutes.

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