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Thread: IAC & idle trouble again.

  1. #11
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    Messes up, like the IAC is dropping to 0% at 0% TPS, and RPM is increasing for every time I accelerate, not idling down to target RPM. Idle function just stops, sometimes you hear it really sucking air through past the IAC valve.

    TPS RoC, what is RoC?

    I know I'm dumping in a lot of fuel. I had a bogging when driving around when outside temp was about 32°F/0°C. I'll get on with my tuning when my idle is under control. It's hard to drive around when the engine suddenly revs 1500 RPM+, especially with stick, unexpected burnouts happen.
    Last edited by fullthrottle; 05-14-2018 at 12:07 PM.

  2. #12
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    Quote Originally Posted by fullthrottle View Post
    TPS RoC, what is RoC?
    Read page 10: http://documents.holley.com/techlibrary_199r11259.pdf (Holley Sniper EFI Help Manual - EFI Software, Tuning & Datalogging)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  3. #13
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    As a test, try this Config File. I changed your MAP scale and some IAC settings.

  4. #14
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    Quote Originally Posted by 81 TransAm View Post
    As a test, try this Config File. I changed your MAP scale and some IAC settings.
    Thanks, I'll try it and come back with a datalog later today. Heading off to work now.

  5. #15
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    Not even 5 minutes driven, IAC opened and sucked air like you would not know. Then IAC dropped from 8-10% to just stay at 0% at idle, TPS 0%. I had a datalog, but forgot to stop it before I turned off the ignition. I restarted the engine, and all was fine again, but thermal expansion had done its job, and IAC was now 12-15%. So I took my screwdriver and adjusted IAC down to 3-5%, and drove off. Ran mostly fine, until a good pull, and suddenly after IAC is down to 0% again, and idle RPM is running wild from there, starting just over target idle RPM, and increasing without control. I managed to get a datalog out of the last run after adjusting IAC, and also a short video showing my display. Short said, its like it just stops using the IAC valve, but when driving on, the IAC goes to parked position 10% until TPS is 0 again, then also IAC drops to 0, and does nothing. Until i restart.

    This run is with TransAm's "Test #1" config: YouTube: https://youtu.be/ZLy_LXAAGcs. Attachment 3135
    Last edited by fullthrottle; 05-15-2018 at 04:08 AM.

  6. #16
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    Always save a Config File at the end of your datalogs so we don't have to guess at your settings for those datalogs. Your video looked like normal function to me. In your datalog you were at 1-2% throttle and it looked like you were letting the clutch out. I believe the system is in idle mode at 2% & under, so as the RPM comes down because of the load from the clutch the IAC shoots up to keep the RPM up. Then as you give it a couple more % of throttle and it comes out of idle mode, the IAC is way too far open and the engine feels like it takes off on its own. There was another spot in the datalog when you were backing off on the throttle. It got down to 2% and the RPM was above your target idle speed, but the IAC jumped up. That would have made the engine surge. I don't know why it did that. Maybe a software glitch? Under your IAC Control you could try changing your Control Type to Slow to see if it has any affect. As a second test, you could disable your Idle Spark control and then lower your target idle speed to 650, then set the actual idle speed with the idle screw to 800. That way the IAC will always want to be at 0 at idle and low loads with the RPM below 800.

  7. #17
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    About the Config File, understood, I just thought it was adequate to refer to your previous config you gave me. Thanks for that, BTW. I will read & understand your comment a bit later, now I really need some food.

    From your Config File (Test #1.sniper) it didn't change anything at all, Idle still acts like it just stops working. IAC % is changing, but IAC valve doing nothing but random stuff. Sudden opening of venturi, letting a lot of air in, you can really hear it sucking air.

    https://youtu.be/RE9tBPoGEUs. Here's another video, here it has also stopped working, IAC % shows normal, but IAC Valve does nothing. Here I have a "stuck" high idle. Restarting and everything is fine. You can also see it's open loop and not Learning, but as soon as its restarted everything is fine. A couple of more logs with config files: Attachment 3138

  8. #18
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    At the end of datalog 10, it looks like the RPM is hung up at 1500 and the TPS & IAC are both at 0. Is this correct? I can't remember if you have replaced the IAC. Have you checked the wiring at the IAC plug? Have you tried unplugging the IAC and setting the idle RPM to 800, and driving it without the IAC operating to see how it acts?

  9. #19
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    Yes, this is correct, also what I'm trying to show with the video on YouTube. I have not replaced the IAC, but it's one of the next things to do I guess. I've tried to set the IAC Control Type to Slow as you instructed, and also lower target idle to 650 and set the actual RPM to 800. Both of these did nothing about my problem. It's still randomly halting all IAC control activity until I restart. I did check the wiring, and it looks OK to me.
    My tire blew off the bead right now, so I have to wait until tomorrow before I can continue to test. Then I'll unplug the IAC and see how it operates. My shop is all out of the IAC, so I have to wait for the next shipment from US to get a new one. If I not butcher another Sniper for an IAC, I'll see. Hmm, do the FiTech have the same IAC? No one wants the FiTech, but Snipers sell like you would not know.

  10. #20
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    Measure the IAC to see which one you have. I believe the Holley IAC is a Chrysler, which is the middle IAC in the attached picture.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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