IAC adjustments won't stick.

Nikkormat · Post by **Nikkormat** » Tue Mar 15, 2016 3:35 am

I've done the IAC adjustment four times now and every time It runs and idles fine for the first start after adjustment. And on the next start the idle returns to 1500 RPM hot. The AC trigger is not on, and I think I'm doing the ISP correctly. What am I doing wrong?

AwesomeJ10 · Post by **AwesomeJ10** » Tue Mar 15, 2016 8:22 am

Use Bill's version of the ISP from his website.
The one that I was using was a very short and condensed version of his and might not be right.

BTW - I 'wheeled the honcho the other day on both computers that you soldered. Runs perfect and I did NOT do the ISP after changing computers and it idles fine.

Check for vacuum leaks in conjunction with Bill's ISP.

Nikkormat · Post by **Nikkormat** » Tue Mar 15, 2016 6:51 pm

Glad to hear that those computers work!

I messed with it for hours today, I even tried using the GM iac adjustment procedure.

So I did the ISP, set the idle to 850 in neutral, and left the IAC disconnected. Runs great.

Is there any problem with not having IAC?

shimniok · Post by **shimniok** » Wed Mar 16, 2016 12:43 am

Hm... maybe I am missing something but 850 seems a bit high with IAC disconnected. That means at fully closed, the lowest rpm IAC can achieve is 850. I'd think you'd want idle set to 650-750 so that the iAC has to be slightly open and thus can shut down to lower idle or open up to raise it.

It could also be something else causing it to run 1500. For example, is it in diagnostic mode, perhaps, due to whatever you have plugged into the ALDL socket?

Nikkormat · Post by **Nikkormat** » Wed Mar 16, 2016 3:35 am

As it sits, I drove the IAC closed as if I were going to set the base idle speed. I then unplugged the IAC and set my desired idle speed. I never plugged the IAC back in. It is fully closed and disconnected from the wiring harness.

FSJ Guy · Post by **FSJ Guy** » Wed Mar 16, 2016 8:16 pm

Once you set the idle speed with the IAC disconnected you're supposed to plug it back in. If it runs wonky after plugged back in, something is up.

You're not running the 10K resistor in your ALDL cable, are you?

AwesomeJ10 · Post by **AwesomeJ10** » Wed Mar 16, 2016 8:27 pm

I don't think he has an aldl cable. He was using my moates earlier

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Nikkormat · Post by **Nikkormat** » Wed Mar 16, 2016 10:08 pm

FSJ Guy wrote:Once you set the idle speed with the IAC disconnected you're supposed to plug it back in. If it runs wonky after plugged back in, something is up.

You're not running the 10K resistor in your ALDL cable, are you?

Nope, no resistor.

After setting the IAC it will idle properly for one start. The next time I start it the idle stays up around 1500 RPM.

Nikkormat · Post by **Nikkormat** » Wed Mar 16, 2016 10:28 pm

The base idle speed in the bin is 650.

The target idle in the bin at 70-100°c is 850 RPM.

Nikkormat · Post by **Nikkormat** » Thu Mar 17, 2016 12:54 am

And yes, the engine is up to operating temperature when I am making adjustments.

It seems like the IAC is fully open whenever it is connected and not driven closed in ALDL mode. Could this be a problem with the bin? Wiring?

I'd really like it to run properly before I put 2000 miles on it next week...

Nikkormat · Post by **Nikkormat** » Thu Mar 17, 2016 5:55 am

Could this be a CTS problem? The readings in WinALDL were spot on the entire time we were data logging.

AwesomeJ10 · Post by **AwesomeJ10** » Thu Mar 17, 2016 8:14 am

I was playing around with setting up a 7427 in the honcho, but after I've thought about it, I don't have enough time to get everything I need done AND play with tuning before moab.

In other words Nikkormat, you can swing by this weekend and grab that moates. I also think you may consider using another ECM. I have two 7747's and you can have one of them as I"m trailering and don't need a spare until I hit the trails.

Until then - read up on Bill's site more about IAC adjustment. I think you may need to tweak the throttle plates and get them perfect, THEN set the ISP.

FSJ Guy · Post by **FSJ Guy** » Thu Mar 17, 2016 9:21 am

Did you instal your Coolant Temp Sensor yet? If not, the computer will think the engine is cold and will always be in enrichment mode with higher idle and (wait for it.... :- p ) richer fuel mixture.

AwesomeJ10 · Post by **AwesomeJ10** » Thu Mar 17, 2016 9:25 am

Yes, he did and it works.

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Nikkormat · Post by **Nikkormat** » Thu Mar 17, 2016 3:55 pm

Yeah I just tested it too and it's fine.

Looks like I'm going to have to stop by Blake.

Bill usn-1 · Post by **Bill usn-1** » Thu Mar 17, 2016 11:27 pm

Hard to keep up when you guys post on multiple sites.

Nikkormat · Post by **Nikkormat** » Thu Mar 17, 2016 11:31 pm

Sorry bill, I was moving over to Binder Planet with a little more detailed description of what's going on and the troubleshooting I've done.

shimniok · Post by **shimniok** » Wed Mar 23, 2016 8:08 am

So just eliminate stuff one at a time. I might start by testing IAC and wires to it. Then try different bin (I can email mine just txt your email), then chip, then module. I have spare 7747 and 27sf512 you can borrow.

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IAC adjustments won't stick.

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