97 Blazer cutting out

Hey Guys,
I appreciate any help you can throw our way.
97 Blazer, 4.3 V6 has a miss big time. 159,000. We started by replacing rotor & Cap,
then fuel filter, the Throttle body control, then did plugs and plug wires. We also pulled the ERG? and relaced the gasket, cleaned it up good.
Still misses, although less when it is in overdrive. You can accelerate, and it will smooth out, temporarily. Not dying on us.
It runs pretty smooth once it warms up. But if cold at all(running less than 45 minutes) it cuts out big time.
Especially in 3rd.
Codes that flashed last Tuesday night, were PO300, PO420, and PO440.
Since then we have gotten a ERG code(can't remember number, info at home)
The PO300 went off for a few days, and now is back, even after we did plugs and wires.
My husband is a good mechanic, but this is getting expensive and he is getting REALLY frustrated.
Any ideas????
Thanks SO much!!!!

i'm definatly no mechanic, but my car is doing the same thing. we had a spark so its firing, we replaced fuel filter, and cranked it with the hoses disconnected, and no gas coming through. did you try that? i'm taking mine in to a shop today to have them check the fuel pump.
when i accelerated, it'd hesitate, then go. it finally died yesterday, once temporarily, then for good at walmart.

also, you might search "fuel pump" on the blazer forum, there are some good posts of how to check certain things related with the fuel system.
ie, ECM batt fuse, fuel pump relay, amp draw, direct fuel pump test, stuff like that. helped a lot. mines a 96 V6 4x4 S10 and i've had numerous problems with it. i'll prolly end up taking it to a shop anyway.

anyone else?

Anyone? Thanks in advance!

My '97 did the same when cold, and would sputter when lugging the engine.

Replaced everything, cap, rotor, wires, plugs, etc...

finally put a new AC Delco distributor (which came with cap and rotor) on it, and all is better now.

Thanks!!!!! worth a shot...