1993 K2500 454 Cold start surge - HVAC control head some lights blinking

[WarWagon]

This is my buddy's pickup that I helped out the other year. Just put a new battery in it and I am told replacing the O2 sensor helped in the past. He has chased this a few years and now it's this bad. Aftermarket muffler is the only change over stock. (It may matter: it's NOT been over 45 MPH since the battery was put in.)

No, it's NOT running out of gas with today's insane prices. Seriously it eventually settles down and runs fine with the "Idle at 45 MPH" warm up mode.

After running a few min it runs fine... cold start surge gone after running some.

And HVAC control head indicating problems I guess.

 

[MrMarty51]

That sounds to Me like the idle air control valve might be binding some.
They can be removed and cleaned.

 

[dbrannon79]

Idle air control valve is probably carboned up. GM was notoriously for this. it also has lost it's memory and needs to "learn" the engine again. best thing to do is remove the throttle body and idle air control and clean well. then reinstall. drive for a bit and it should resume normal operation once the PCM re-learns it's engine. I have seen many that do this even the newer trail blazers, once PCM memory is lost it can't re-learn on a dirty or carboned up throttle body and parts. once clean and codes cleared it will settle down lol.

as for the AC flashing. iirc the damper door motor is out of spec and ether needs to be repositioned or the actuator motor replaced. reset the AC control and all should be good once again.