I have a 1994 S-10 Blazer with a 4.3 Vortec and 118,xxx.it ran great for about a year after i got it,then it had the starter replaced,ever since then it seemed to not fire/miss on 1 cylinder.I just replaced Wires,Plugs,Distributer Cap,Coil Pack,and fuel filter.I was told it could be the EGR Valve,took it off, was a little dirty,but the little rod thing went up and down perfect.When i replaced the plugs 1 of them was a lot blacker and crustier than the others.i ran it with the new tune up for about 10 miles than pulled the plug from the same cylinder and it was fine.:banghead:It still runs fine,it just seems to hesitate/shimmy a tiny bit.Im out of ideas.Any help would be greatly appreciated.

4.3 w(center port fuel injection) or z(tbi) ? makes difference in trouble shoot procedure

if you mean the 8th VIN # its W.Thanks.

What brand of parts did you use when you tuned it up? Which spark plug was fouled? Is the SES light on? Have you checked fuel pressure and leakdown?

I used Autolite Platinum Plugs,and i believe autolite wires,and cap.it was the first plug closest to the front on the passenger side. the SES light is not on,and i have not checked fuel pressure or leakdown (dont know how :)).i did putt some heavy duty concentrated injector cleaner and ran it for about 10 miles.i believe the spider injectors were replaced long before i bought it.Thanks for the replies.

Have you tried doing a manifold vacuum test ? Might show wether or not you have a slight vacuum leak. Check exhaust manifold gaskets for leaks also.

Just a few thoughts.

Autolite Professional Series wires are one of the best wire sets money can buy however, lose the Autolite plugs. Use AC Delco ONLY, the 4.3 is very fussy when it comes to plugs.

we did a compression check and everything was fine.Does the plugs matter that much?were going to check the injectors today.

Okay,2 of the Injectors weren't seated down right so fixed that,replaced the fuel regulator,it seems a little better.Should i replace the plugs with ACDelco?Thanks.

Should i replace the plugs with ACDelco?Thanks.

Absolutely. These trucks prefer them.