ok this is not a blazer but there seems to be a ton of knowledge on here so here it goes i have 2nd gen 94 s10 truck it has a 4.3l cpi motor,ive only had it for 3 months and in those 3 months ive been putting a new front clip and odds and ends done for inspection so i got it running good and everything so i took it to town and it started to surge at idle almost like a chug if you go over by the exhaust but i still passed inspectionbut now i cant figure out this problem ,when im driving i can feel almost like a slight jerk,tug,buck whatever you want to call it and its when i hold the pedal steady.Now here is the strange part it only does this when it starts to warm up,i put in new ac delco plugs,wires,distributer cap and rotor with no change,all my old plugs were brown just like you want them and this thing has no power loss it runs really hard and has surprising power for a v6 so i guess that rules out a clogged cat.it had no check engine lights no smoke or black soot coming out pipe like most the problems ive read about,i peeked inside the plenum and it was tarnished like you want it,there wasn't any fuel smell,puddles,or washed out spots so i guess the spider and regulator are good,i have been told this thing has a limp mode so i unpplugged the temp sensor and it didnt really change the way it ran and i also unplugged the 02 and it still surged,i cleaned the iac valve and no change so now im thinking maybe the tps or map but why would these fail when the motors warm?i even checked for arch jumping at night and there was none im out of ideas besides checking fuel pressure,also cleaned the egr and that didnt help so i unplugged it and still didnt help

 

im having the same problem and i think it might be my intake tuning valve im not sure but in mine my flap in the intake you can move it back and forth with no resistance so im not sure...i will be keeping my eye on this thread to see what you can find out and maybe we could get it fixed....

 

I would still do a fuel pressure test just to be sure. Have you checked for any vaccum leaks?

 

yes i have tried to find vaccum leaks and found none when you pull the brake booster line off it idles high so i think it has good vaccum

 

im pretty sure the tuning valve doesn't have anything to do with idling i heard it helps you get better mileage but i could be wrong

 

well i get 19mpg with or without the ac so i dont know what else it is passed emissions with a fast pass test it was so clean