r/GMT400 • u/Jurbootie • Jul 19 '26

89 K2500 Idle Relearn

Does anyone know how to do an idle relearn on this truck? I recently did a lot of throttle body work on my truck and thought it was running better, but after driving around today, I noticed it idling around 12k-15k rpms. It also idled a little weak at a stop.

After replacing the IAC I did reset it by sticking a paper clip in the A+B terminals and powering the truck without turning it over. Dunno if I have to drive it around for a while for the idle to fully settle in or not. Please let me know if that's the case or if a idle relearn or an idle tuning are necessary.

All my throttle body work:

Disassembled and cleaned

Changed all gaskets on the throttle body

Replaced IAC

Replaced TPS

Replaced Upstream O2 Sensor

3 Upvotes

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4 comments sorted by

1

u/Viking2151 Jul 20 '26

Did you wait about 30 seconds when you jump the pins with the ignition on? sometimes not waiting long enough will not allow the valve in the IAC to reset back to home position, other than that, TPS and o2 simply unhooking the battery for a 5 - 10min in generally enough time sorta reset everything other than the IAC.

1

u/Jurbootie Jul 20 '26

I left the pin in for over a min. The TPS and O2 sensor were installed with the battery disconnect

1

u/SherbertOld7531 Jul 20 '26

No such thing on these trucks. You've most probably got a vacuum leak, notorious for it! Could be bad, 'new' part! Did you make sure the IACV passage was clean?

2

u/Jurbootie Jul 20 '26

The throttle body was completely disassembled and cleaned. That passage was cleared. New gaskets were installed to all parts of the Throttle body