So let me start with everything I’ve done to this blazer, rough country 2 inch lift sealed from 3.42 to 3.73 gear ratio while I was doing lift I did pitman arm, ideler arm, tie rod ends, wheel bearings, cv axels, and leaf springs to tighten up the 26 year old suspension with 160k miles on it and the blazer feels great down the road. Let me say that I am over cautious with my things and I notice issues fast and like to dig deep, but I’ve replaced my fuel pump, fuel filter, and swapped from old poppet injectors to the new style injectors and the old rig just purs great but there’s one problem, when it has a warm start but it sits for like 10 minutes or so it fires right up but has a super low idle for like 10 seconds and it fixes itself and boom it’s fixed but I like my **** to be perfect i get it’s an old rig but i want it to drive like we’re still in 98, so my initial thought was a loose fuel line so it looses pressure but then i would imagine it would be a long crank on cold start but it doesn’t so i dont think its that and before i did all of the fuel upgrades it didn’t have this problem so i was wondering if anyone else has seen this before, next up is probably my idle air control valve and to see if it possibly got messed up with taking off throttle body??

 

iac, good guess, thats what it does. Manifold or tb leak should make high idle not low.

Is the exhaust blowing fuel out when it idles low? Smell at the exhaust tips.

Check the injector spray pattern with a timing light connected to the coil wire. That will strobe the fuel spray so its visible. That might catch an injector problem.

 

Not sure how you are supposed to check the injector spray pattern?? Maybe DaveCa thinks that a 1998 Blazer is TBI??

Seems it is one of your "fuel upgrades" that is causing the problem since it did not do it before. If you jacked with the throttle body/IAC, then there you go.

Look at counts for the IAC. IAC should be backing off (opening) when you shut the vehicle off. Then when you start it it should slowly come down to a proper idle. Potential problems are mods/damage to the throttle body, sensor inputs (like TPS) that the PCM doesn't like, IAC itself, and turning that damn base idle screw.

What is the TPS reading at idle and then again at full throttle (specify % or degrees or volts)

Good luck and best wishes for a successful repair.