I have a 91 2.8L, tbi, 5 speed s10. This truck has been great to me but recently has started to have a problem. Sometimes when i start it its ounds really weak and i noticed that it seems that not all the cylinders are firing. Then all of of a sudden all the cylinders fire like normal. At first it was only happening during random start up but recently it started to do it while on the freeway. When this occurs you can feel the engine surge and the power drops and comes back its very scary. I changed the cap, rotor, plugs and wires. Is there anything else that might cause this. The truck does not die out completely so some cylinders continue to fire. So i figured it was not the coil, maybe i'm wrong. I appreciate all help, this is my daily driver.