Need help truck is mis firing

Hello Everybody, I have a 1994 s10 4x4 4.3l z motor
My truck has developed a misfire (I Think). The problem is starting under a load the truck will stumble and backfire through the throttle body and also at highway speeds the tach will jump up 100 to 200 rpm consistantly. Below are thing I have replaced.

wires
plugs
cap and rotor
TPS
ignition module
fuel filter

I am changing the pickup coil and regular coil tonight. Could this be fuel related?

Thanks Everybody
Mark:banghead:

Had a similar problem with my S10, changed the coil and it's been running great since.

Thanks joshmitch05
I am changing mine coils tonight. I will let you know. Mark

Hello
We I changed the coil and the pickup coil and it still does the same thing. I need help

I've found that the injector spiders (inside the intake) can cause this problem..one guy I know replaced his motor and later found out that the injector's were the problem..of course they aren't cheap but I think you'll find your problem there..

Sorry,
My truck is Throttle body injected and the injectors are only a year old. they seem to be working fine.

The closest thing to this problem I have encountered with a TBI motor was the pressure regulator in the TBI..poor quality gas and water had rusted the spring into two pieces,, the thing would run fine some times, then spit and sputter, not go over 45 and just quit once in awhile..I replace the regulator and that fixed it......Hope that helps,,,some of these things can be a nightmare...

I replace the fuel regulator last summer. I am going to replace the vacume line tomorrow and clean the Egr. I will let you know if this helps.