'94 Chevy z71-- misfire
 

I have a 1994 Chevy k1500 with a 5.7L. After 230,000 miles i did a motor swap from a totaled donor vehicle. My truck runs good most of the time. Except it will randomly cut-out and sputter. The truck has new spark plugs, cap & rotor, coil, egr, knock sensor, and throttle pos sensor. When i made the swap i kept my original throttle body. This problem may have been there before the motor swap, just not as bad. Its been through the shop, its not throwing any codes, except every once in awhile service engine soon light will come on but never more than a few seconds.. Im stumped.. the shop thinks it could be my catalytic converter.. but i think there just giving up.. any ideas?

double check every connection on every sensor first. had an s10 that had a bad connection on the temp sensor. it would rattle loose once in awhile, causing code to come up and truck ran like crap. also, make sure fuel pressure is good, should be around 11-13 psi if memory serves. check all power connections at battery, starter, junction box/block, all grounds. you can do a general check on cat as well. wait till dark, start and run truck around awhile, gettin up to operating temp for a bit. stop, look at cat converter. if it's glowing at all, change it. BUT, even if it doesn't glow, it could still be clogged, generally tho, your problem won't be intermittent. good luck, keep us posted

thats good point.. the way my truck goes from running perfect to horrible then back to perfect does seem like a connection issue.. one note to add.. i did snap my ground wire on the back of my block when i pulled the motor and never replaced it..

def replace that ground. still check everything else too. hopefully you find it easy enough.

An easier way to replace the engine to firewall ground strap is to take a #4 negative cable from the passenger side head at the dipstick bracket mount bolt to the passenger side firewall. Re-attaching the cable in the OEM position now may be difficult.

well thanks.. you just answered my second question.. is #4 negative cable what the stock grounding is made from? and i should be able to find this at any napa right?

battery cables can be found at any auto parts stores.