I have a 2000 Chevrolet Blazer 4 wheel drive with just a little over two hundred thousand on it. On the way to work it started missing real bad had a similar problem before it was the distributor cap well replaced it ran a little bit better still has a slight Miss at idle check vacuum hoses everything is good replace mass air flow sensor replaced plugs and plug wires replace EGR valve has good compression valves aren't sticking or burnt don't have cracked head or blown head gasket. It has ran like a champ over the years and it all started the other day with that distributor cap going bad again I've changed about everything that I could possibly think any help would be greatly appreciated it don't seem to do it all the time when you first crank it it don't miss that bad but after you drive it for a little while it seems to get worse Has a Miss and it says it's missing on cylinder 1 im stuck here ?

 

sounds like it might be running lean, do you have an OBDII Scanner thats able to check stuff like fuel trim and see live data from the computer?

 

From what I have learned here, anything but the AC Delco distributor parts can be troublesome.

Did you see any damage to the old distributor cap?

Did you check the spark plug wires?

 

Try cleaning out the fuel system and check your temperature sensor plug on the driver side of the engine. Mine was missing bad when I got it back in November and I tried everything to fix it then found that wire.

 

My 99 zr2 blazer with the same stock w block has a good 20' of vacuum line and several gaskets along the intake manifold plenum, so my advice to you is replace ALL of the vacuum lines, do the upper plenum gasket that has 4 possible air leaks 1the main manifold gasket 2the oval ring gasket that fits over the spider injection assembly and 3the 0 ring to the vacuum port on top that goes to the brake booster 4 the map sensor has a small ribbed gasket which on mine took forever for me to figure out it was bad and while you have the top plenum off replace the fuel regulator which can drip gas out of the vacuum port on the side of it the hole fuel regulator is inside the intake manifold on the back of the spider injection system.... take your time, normally I'd say change one part at a time but with high mileage these 4.3 engines suck lots of air from lots of places gaskets were out hoses get brittle, no code misfire are usually one or both of those things it's worth fixing that 4.3 just keeps on running

 

Only other thing I missed is make sure you have no plug wires touching any metal or other wire along their route 4.3 is picky about that

 

that sounds more like you have worn out wires with bad insulation..