Good day to you all...I have my 12 gauge loaded, and its pointed at the engine block as we speak. I'l start from the beginning...I have a 89 blazer, 5.7 TBI, engine is new to vehicle. I bought it around 3 months ago, and I've had the same issue since purchase. If i floor it, or have 1/2 throttle, it runs like a dream...but when I'm "feathering", or lightly touching the throttle, it hesitates, sputters, and sometimes dies. It only does it sometimes, and some days are worse than ever. If I shut it down for a few minutes, problem goes away for a while, then comes back. It is throwing code 43, the ESC module. Heres what i've done/replaced so far:
New- TPS, IAC, O2 sensor, Knock sensor.
Rebuilt the TBI (its a holley 502-6), all new fuel springs and gaskets, checked all vacuum lines (all good), injectors seem ok, equal fuel flow and pattern.
So...any ideas? I could spend the money and buy the ESC module? I've heard those hardly ever go bad...MAP sensor seems ok, when I unplug it with engine running, I have a change in idle/smoothness. I'm at my wits end with this issue, any help would be greatly appreciated...thanks.

 

Have you tried changing the egr valve? I've had the same problem with my 93 blazer for a while. I've changed the tps, the map sensor, the egr, the o2, did the whole tune up and I still get the issue but only upon my initial start up. If I run it around the block and shut it off and start it again the problem goes away until it's cold again. The last thing I did was the o2 sensor and in my case it was the most fix I've seen so far.