bad issues with swap

[trk698]

hello everyone how are all of you doing,
i have a 93 ext cab 2wd 5.0 tbi chevy silverado iam having so issues with it well i took out the original 5.0 engine only replaced with a vortec roller 5.7 liter purchased new manifold from gm that let me keep evrything the same computer, harness, etc. swap is done runs great sometimes but i get alot backfire thru the tbi and exhuast when i get these backfires i lose alot of power from the engine engine light goes off run like crap till engine light turns off runs fine after it is a everyday occurence engine codes i get are 42,35,21,12 check timing replaced o2s
injectores in tbi everything is all new except tbi i cant get backfiring to stop all out of ideas any help would be greatly appreciated thanks in advance

[amac209]

did you unplug the spout connector when you set the timing? code 42-electronic spark timing fault.
21-tps doesn't agree with map(voltage above 2.3V wile map is above 15psi)
35-iac fault
12-no distributor pulse(this is always given while in diagnostic mode)
i've heard you need prom(programable read only memory) for a 5.7 and injectors
i think most of your problems are related to the timing make sure you unhook that wire first and plud it back in when done. try unhooking the tps i had to do that on my truck when it went out. the cel will come on and the engine uses the map instead. hope this helps you

[trk698]

i did unplug the spout the first intial time that i put in time for some reason the backfire continued but very light truck was very drivable
a week later it started to do it again and i checked the timing this time
i think it was 12 or 13 degrees retarded so i put int back in time again but i forgot to unplug the spout the wierd thing is i put a pro billet msd distr. first time i did the timing work great tightened down distr. why would it go out of time again and the distr. was not loose at all very tight

[tblentrprz]

Did you get it figured out? I'm working on a 89 that won't run with "set timing connector" connected. Please reply. Thank You.