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There are a few methods floating around, but this is the one used by GM techs (OBD1 method).
- Reset ECM by pulling ECM fuse (underhood) for a few seconds.
- With A/C turned off, start car and immediately put it in Drive
with your foot on the brake. If the car does not start initially,
keep trying WITHOUT putting your foot on the accelerator.
- Idle the vehicle in Drive for autos and neutral for manuals until the coolant fan has cycled on then off for one minute.
- Shut off the car for 10 seconds.
- Start engine, place in drive and let idle for 5 minutes.
- Shut off engine.
- Idle is learned.
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Works perfectly!
Works perfectly!
1. disconnect battery for a few minutes
2. Connect battery and try to start car.. it should stall out.
3. Re-start the car and leave it alone while it idles up and then back down. Once the idle has settled it's fine. You can watch all this in a datalog.
The ECM is just extending and retracting the IAC motor on a timer, it assumes that after it's fully extended, then fully retracted that the stepper motor counts are correct. Many industrial machines use the same logic as long as there isn't any damage to be had from over-extending or retracting the device. I see it used with electric rams daily.
it is nice to see someone from GM here though, Welcome!
even with the huge cam my 3500 idled like a dream. IAC counts stayed between 20 and 40 with the MAP around 60 Kpa, 1100 RPM.
Go for a drive. Let the fan cycle a couple of times.
God knows the tune on my car is frankenstien enough to confuse anyone, but OBD-1 pics it up and the car runs just fine.
With all the crap done to my car I have never had an issue as long as you use good parts.
TCE TB, Delco TPS and IAC, and just let the ECU get used to it all.
My car will idle all day without an issue.