Misfire

97 s10 blazer 4.3l

I was wondering, my truck misfires at about 2000 to 2400 rpm also worse when it rains but is always there, only in this range could this be my cat. also my idle has gone up about 400 rpms would this happen from a bad cat. and when i hit the gas i hear a little rattle from the cat.

probablly not. I'd say it probablly needs a full tune up (plugs, wires, cap, and rotor.) Use quality parts so you only have to do it once. I suggest AC Delco.

yea i have done all that even replaced the coil. also about a year ago i had problems with it starting for about 6 months and it ran like crap. finally it kicked out a bad fuel injector code. i replaced it but i had driven the car like that for a while i figured that it could have pluged up the cat

how long ago did you replace the cap/rotor/wires? I had a similar problem on my 97 4.3L, where it would misfire, especially in the rain, usually under light load. Make sure there is no carbon buildup on the electrical connections for the cap and rotor. If so, clean them off and use a bit of dielectric grease. You might just need to replace the cap altogether because if it is cracked, moisture might be getting in there under the seal causing galvanic corrosion, and leading to a misfire.

i replaced them about 1 1/2 agomsd cap accel rotor. it was doing it before that also, it has just gotten worse. its wierd cause like i said its around 2000 rpms. i will probably do a complete tune up again. might change the cat also carbon is coming out with the water from the tailpipe. and there is also a rattle from inside the cat.

The carbon just confirms what you already know, that you have a misfire.

It is hard to say without a hands on diagnoses what continues to be your issue. I suspect a fuel pressure problem could also be part of it.

I would suggest a scope check at a repair shop with certified techs. I could always find a misfire on a scope, and usually tell whether it was fuel or ignition related.