i got an 03 s10,4.3l v6,2wd,automatic.im having what might be a misfire,or maybe a fuel problem.i just do not know.it runs fine around the neighborhood and thru town.but when i get on the hiway,and if i have to pass on an incline,check engine comes on,it looses power,acts like bad gas,if i have it scanned when check engine light is on,it shows 4 and 6 cyl.,s are misfiring.plugs are new,plug wires,new.new dist. cap too.fuel filter was checked and its good.fuel pressure is at 50 psi.im hoping to gain some good information on this forum.i sure would appreciate any help.

 

well the computer is trying to help you find the problem when the CEL comes on. It means it recorded a fault, which you can scan and analyze. I would start with a full diagnostic scan and narrow down the problem rather than randomly throwing parts at it.

Usual suspects for lack of power on the highway is failing fuel pump, or clogged cats.

I'm not sure that idle fuel pressure is a good indicator that the pump can deliver volume at full throttle.

 

thx for writing.i did take it to local dealership after other shops could not help.they scanned too... it and said coil is the problem.i replaced it.i do have a new cat too.also,other shops scanned it and it read a misfire with #6 and #4 cyl. plugs,wires,dist.cap are all new.truck has only 165000m.i didnt even think it might be a failing fuel pump,as it runs really well thru town,as long as im not on an incline and really pushing it.

 

What was the code? I don't think there are any faults that specifically say "coil is bad".

yea you'll want to measure the fuel pressure and check the filter if it's accessible
Not sure if you have electronic or dizzy ignition, but check the retard.
These engine are also notorious for failing intake gaskets. (cyl 4 & 6 are neighbors)

I'm really surprised two shops could fix your car. Sounds like you need to find a more competent mechanic.