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Hptuner failure & IAC

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Old 08-10-2018, 03:44 PM
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Default Hptuner failure & IAC



Unit used less than 10 times.
Long story short I have an mpvi2 that is on way back to hptuners. Fairly certain unit is defective. However here is what happened. The unit was having issues connecting. I figured it was my side of things so I uninstalled and re installed software.
I reflashed car after making some adjustments to throttle cracker and as it was writing and doing its thing I washed the car. I open the door and it was done. I start the car and immediate very high idle. Like entire brake booster hose was off. 3000rpm. I was like oh man. I pulled car into garage and thought maybe this unit is going bad. I tried to do a reflash but unchecked the high speed write. It started to erase and failed mid erase and car wouldnít start. After about a dozen controller unlocker errors I wound up disconnecting the battery and opening vcm editor from original folder and it finally reflashed. The high idle is stuck there and I start trouble shooting this. Iac valve is fully retracted and it will do nothing but vibrate when I command different counts in the scanner. Even a new ac delco will do nothing. If I manually pull out iac valve and disconnect and reinstall the car idles pretty close to set rpm. Iím almost certain itís not a mechanical issue but a software/electronic fault. I hooked up the mpvi2 to laptop today and it wonít even recognize. In the mean time has anyone had this happen? Should I go ripping into the iac harness or do you think a clean write with a good tuner will fix this? This is incredibly frustrating and stressful so I guess Iím just fishing for someone elseís experiences. Also considered bad pcm or iac drivers? Connectors on pcm harness are red/blue.
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Old 08-10-2018, 05:20 PM
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I got this from the sloppy site:
​​​​​​​
IAC Relearn Procedure
If you are having idle issue you may need to reset your Idle Air Control (IAC) and
TPS, do this before you start drilling holes in your throttle body (TB) blade. I have
used this procedure on some huge cammed cars and it worked.
1) Monitor your IAC, Idle Speed, throttle position voltage and your throttle position %.
2) With the key in the ON position, adjust your TB set screw until your throttle position
is 2%.
3) Turn your key to the OFF position.
4) Unplug your Throttle Position Sensor (TPS) and IAC.
5) Turn your key to the ON position for a few seconds, and then OFF again.
6) Plug in the TPS and IAC and then turn your key to the ON position and restart
logging. Your throttle position will now be reset to 0 degrees and about .45-.55 volts.
7) Start your engine, your IAC should be 40-60 for a cammed engine.
if you are not at your desired IAC position redo the above procedures in smaller
increments.
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Old 08-10-2018, 07:33 PM
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Everything was already dialed in. Had 55 counts at 210 fans off. Just wanted to adjust a small drive ability quirk and wash the car. Always something
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Old 08-10-2018, 08:03 PM
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if the only thing changed was the tune, reflash an earlier copy?
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Old 08-10-2018, 10:07 PM
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Well I tried that. But Iím thinking that the pcm may have been compromised and I canít do a write entire cause Iím afraid it would Brrick it
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Old 08-11-2018, 08:21 PM
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After failed googling does anyone know which sensors the pcm uses to control the iac valve? Iíve lost my multimeter so not sure on wire continuity yet but at this point Iíve determined with iac unplugged and extended out to a certain spot car runs 100% normal. Iím just trying to button up any stupid little thing it could be before I get my hptuners back. Also to check the iac harness can I just test continuity between the two circuit drivers at the harness or do I have to pull pcm pinouts??
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Old 08-11-2018, 09:18 PM
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Do you try re setting your iac? Imo it is working fine. The computer is telling it to do something and its doing it. The thing is the computer will tell the iac move x amount of steps and it will move. The problem is were is it moving from. That is why you need to reset it or home it. That way the iac. For example the comp commands 25 steps, the computer is assuming te sensor is at 0 steps and has no way to verify this. So if the sensor is sitting anywere other then 0 it will still move 25 steps, but will end up in a different position and give you drama.
I think when your write failed, your iac home was set incorrectly for whatever reason.
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Old 08-11-2018, 10:09 PM
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It seems like it isnít extending or closing airflow and only opening it. Also I donít think ls motors have a procedure for initial iac set or install??. From what I thought a key on/off cycle would reset it. But Iíve unplugged tps and iac and did the tps reset as well. If I were to command steps from 0-128 in hptuners the pintle showed no visible movement. Motor would vibrate. That was about it. Iím not sure where to go from this point besides checking the wiring. Car has new IAT,TPS,and now IAC. Also when I would plug in iac after I had it running smooth. Pcm would command iac to fully retract eventually Iíd be idling about 3,000
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Old 08-12-2018, 05:54 AM
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Iac harness to pcm connector showed continuity for each lead. I have no idea what else it could be besides the write error and failed hptuners. Or IAC drivers in pcm...hereís to ripping my hair out. Shoulda went EFI Live
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Old 08-12-2018, 10:27 AM
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an incomplete write could have left out the code to operate the iac driver. try a write entire.
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Old 08-12-2018, 04:05 PM
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Yea thatís what Iím hoping for. I was just trying to button up everything I could on my part. It had a slightly high/ slow idle drop due to throttle cracker table needing a small reduction across the table. But I donít think itís anything mechanical at this point.
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