Check and make sure that the brown wire below the glove box and underneath the carpet is not disconnected. (Controls Timing Advance). You could also time the vehical using vacuumn gage and tack along with the timing light. Goal is to obtain highest vacuumn and the best idle speed.(Adjust all timing with the brown wire disconnected) This will optimize your timing.

Ok, truck stalled yesterday at a stoplight. Luckily I was able to push the Blazer into a car dealer's parking lot. Truck would crank, but no fire. Checked igintion coil - good,sending 12volts to distributor. Removed cap and rotor button to inspect - good. Put all back together, sprayed ether into TBI and she started - but rough. Able to get her home sputtering and hiccupping badly. Went to Auto zone & bought distributor . Installed,set timing and WA LA!!!!! Blazer fired right up and had plenty of power. No more sputtering and hesitation. Been doing a lot of reading in this forum that has helped me a lot in troubleshooting. Thanks to all you guys I know have a strong,smooth running Blazer. Time to hit the mud!!

Good deal. Did you look over the old distributor? Were you able to determine what it was that caused it to run poorly? I have seen cracked drive sprockets cause weird issues.

Yes , we looked over the distributor before we gave it to autozone for core. It looked rough and rusty. It had some play it it and the gear was a little worn. I'm guessing maybe the pick up coil was bad. But instead of just replacing parts, heck for $99 I just replaced the whole thing.

I'm having similar problems right now with my Jimmy. Same setup as yours, same year. I've already replaced the cap, wires, and rotor...Same symptoms,

I grabbed an ignition module off my brother's K1500 Pickup with a 4.3 also...nothing changed.

So, I pulled out the distributor core. I examined it and noticed the gear on the end. The spin on the gear is arrested quickly. The gear doesn't spin too freely that, and it seems to be in overall bad shape. But the question is, does the gear not spin well or very freely? 'Cause I think I might have solved it...

no, mine didn't turn to freely, it would hang up a bit and not turn smoothly. Also mine had rust build up around the top where those little "nipples" were on the round part that spins around. Sorry I don't know the correct terms. It is the part the ignition module is mounted to and the part above the pick up coil. Did you check your pickup coil?. I was told that part tells when to spark for each cylinder.

Now I'm not so sure my distributor is installed correctly. I made my marks on the old one and installed the new one exactly the same way. Rotor button was in same position. However when i turn the crank to the position on the vibration damper that has the groove and mark for top dead center at 0 degrees, my rotor button is pointing at position 4 on my distributor cap. If I turn it to postion 1 on the cap my mark is about 2-3 inches to the left of the timing plate gauge. The engine runs good,sounds good, but I just don't feel I'm getting full power.Could my distributor be off a few teeth?

I think that Autozone has the proper timing procedure for your truck detailed. I think I remember reading through it not too long ago. I responded to your question in Tim's (hanr3) post.

Ok, so an update to my little problem...

I bought a new distributor shaft with new ICM. Did nothing. Now it won't even fire, period. I also noticed something strange, I think the TB is shooting too much gas into it. I'm getting a strong scent of fuel when it cranks. I haven't checked the ignition coil yet...But might be the problem. It doesn't seem to be getting spark? I'm not entirely sure. I assume if is not firing then their is no spark, which brings me back to the ignition coil...I swear this is becoming a full-fledged nightmare.

Any suggestions?

You did get the distributor reinstalled properly didn't you...? I would go through the whole engine timing procedure to be sure.