Engine Backfire on Pass Side Bank

[NY_Z28Man]

Well heres what I'm working with. I have a 1993 GMC sierra with a 350 I installed myself out at college. The engine has been fully rebuilt. Bored 55 over and honed 5. Everything interenal basically new except crank and rods. Heres the issue im dealing with: The engine that originally came in the truck was a V6 4.3L. The truck has a 4L60E tranny so I had to use the computer out of the V6 with the 4L60E controls in it. I try running the engine and it seems to have a backfire out of the passenger side only. I was told the ignition timing would be off cause of the V6 computer and V8 engine. so I unplugged the spout and advanced the timing myself, but it still backfires like crazy. The cap, rotor, plugs and wires were all bought new with the engine. I was thinking of a way to put in the V8 computer thinking that will help my problem, but I cant find one with the 4L60E tranny in it also. So if I buy the V8 computer and wiring harnes, is there a way I can make the tranny shift even though the computer is for a 700R4?? I looked at TCU's online but they seem more for aftermarket performance and cost well over 500 bucks. Any information would help my problem greatly. Thanks for reading this, and I really hope I can get this engine running right.
-Paul

[Thunderbolt]

Originally Posted by NY_Z28Man

Well heres what I'm working with. I have a 1993 GMC sierra with a 350 I installed myself out at college. The engine has been fully rebuilt. Bored 55 over and honed 5. Everything interenal basically new except crank and rods. Heres the issue im dealing with: The engine that originally came in the truck was a V6 4.3L. The truck has a 4L60E tranny so I had to use the computer out of the V6 with the 4L60E controls in it. I try running the engine and it seems to have a backfire out of the passenger side only. I was told the ignition timing would be off cause of the V6 computer and V8 engine. so I unplugged the spout and advanced the timing myself, but it still backfires like crazy. The cap, rotor, plugs and wires were all bought new with the engine. I was thinking of a way to put in the V8 computer thinking that will help my problem, but I cant find one with the 4L60E tranny in it also. So if I buy the V8 computer and wiring harnes, is there a way I can make the tranny shift even though the computer is for a 700R4?? I looked at TCU's online but they seem more for aftermarket performance and cost well over 500 bucks. Any information would help my problem greatly. Thanks for reading this, and I really hope I can get this engine running right.
-Paul

I am almost possitive you need the computer from a v-8 truck. As far as the trans goes any Gm 1/2 ton truck from 93 through at least 99 has a 4L60E trans. Someone in 2000 or later it was changed to a 4L65E. The trans should be the same from 93-95. The 92 and older trucks used a 4L60 which is the same as a 700R4, Actually they are different versions of the 700R4. Be careful using a V-6 trans because if it is like the older ones the ones behind a V-6 look the same and work the same, However they have less clutches in the clutch pack than one that came behind a V-8. If you find a 93 Chevy with a V-8 the computer should work.Hopefully someone else will be of more help.

[NY_Z28Man]

Yeah thats what I was thinking. I know the pulsewidths are probably different in V8's and V6's due to the 8's firing every 90 degrees and the 6's firing every 120. If there was a way to reprogram the bandwidths I'd be set. I just dont think thats possible. Some people told me you can switch a computer from V6's to V8's but I dont think that switch exists. If I could that would solve everything but that would just be to easy. ANYONE HAVE A 93(up to when the vortech started I think 95)COMPUTER AND WIRING HARNESS FORSALE????

[2000CAYukon]

If you originally had a V6 and changed to a V8, you need to change the PROM not the whole ECM.

You should be able to find a PROM from a junk yard or get a new one from www.tbichips.com

//2000CAYukon

[me3500]

The transmission operates off the TPS, the computer just tells the motor how to run.

[NY_Z28Man]

Yeah I didnt think the computer read much other then the TPS for the transmission operation. But I do know that the computer controls the transmission shift solonoids(sp).