Need Help - 3.4 to LT1 wiring issues

[Czop418]

Ok Lately ive converted a 3.4 firebird into a lt1. Evrything went smoothly but wiring for the 2 extra cylinders has me stumped. I ran the 5.7 harnes to the 3.4 harness to fire the 2 other injectors. But its still loading up the 7 & 8 cylinders. Please guys help me out. Thanks Rich.

[BonzoHansen]

What did you do? You still have the 3.4 engine harness? I'm confused

[LTb1ow]

Say what?

[transmaro93]

yea whaaa....? did you swap the entire engine harness??

[Czop418]

I combimed a 5.7 engine harness into a 3.4 body harnes. And put in a lt1 ecu. And wired the last 2 cylinders into a hot so it would fire . But now 2 of the cylinders i belive 7 and 8 are loading up any suggestions to get past this ?

[BonzoHansen]

you used relays on injectors?

[LTb1ow]

I combimed a 5.7 engine harness into a 3.4 body harnes. And put in a lt1 ecu. And wired the last 2 cylinders into a hot so it would fire then put them on a relay. But now 2 of the cylinders i belive 7 and 8 are loading up any suggestions to get past this ?

How about a proper harness?

Relays to control injectors... wow.

[Czop418]

Ok lt1 has 2 connectors going to the body harness and the 3.4 has 1. So i took the 2 combined it into 1 matched all the wires , for the 2nd connector had 1 wire in there that i found on all data to control the secondary injectors so i just added a power to kick them on to start the vehicle.

[BonzoHansen]

electrically what you did is wrong. relays are far too sloppy timing wise


You should have made the lt1 harness more or less stand alone

[LTb1ow]

What year PCM is it?

[Czop418]

94 pcm with a 95 ecm.

[Czop418]

And sorry for the typo we never tied it into a relay thought we did. My buddy did the wiring not me.

[LTb1ow]

94 pcm with a 95 ecm.

Hmn, what?

[BonzoHansen]

do you mean BCM? you keep talking body harness

[Czop418]

the power control module is stock form the 94 3.4. Then we used a 5.7 95 Engine Control Module.

[LTb1ow]

So how did you do all the pin outs?

[Czop418]

All Data.

[BonzoHansen]

i think that your friend should step away from the wires.

did he try to integrate the two?


All data? you mean he looked at a diagram & started cutting & splicing?

[LTb1ow]

So you are using a LT1 PCM and parts of a 3.4 harness?

Why the relays?

[Czop418]

Becuase have you EVER tried to replace a WHOLE BODY HARNESS. Its Probable atleast a 15 hr plus job. Now dont get me wrong i have the 5.7 harnes and worse case scenario i will put in the lt1 body harness. But im trying to see if theres ANY Possible WAY wiring wise that DONT HAVE TO DO THAT!

[LTb1ow]

I am so confused.

[BonzoHansen]

You don't need to replace a body harness. I guess I would have made the LT1 harness basically a stand alone harness. what does the body harness need to know, rpm? gotta be a way around that.


And yeah, I've rewired some cars.

[transmaro93]

the harnesses on f-bodies really arent that hard to do... its a big job... but... its better to do things right then Frankenstein up your car... i suggest you start ripping stuff apart and change the harnesses properly... way to much important stuff running to and from those harnesses to screw it up... just my .02 take it for what its worth... with that said... what is it with people trying to save a minute and doing stuff 1/2 asked... first the guy cutting holes in his floor and now this... good luck either way man

[Czop418]

Ok Im going this explain this thoroughly and when you understand this Say OK.

[Czop418]

Ok LT1 5.7 engine has 2 body harness conectors.

A Firebird 3.4 Has Has 1 Conector to body and Engine.

I took the 5.7 engine Harness Plugged Everything In But the Car would not start. So I recently found out , that it was not firing on 2 injectors becuase it was a 6 cylinder. So I went to All Data , I traced the wire diagram from the connectors , I found my main Power wire for the other 2 injectors. And I ran it into 1 connector. The car started started ran evenly but now when it gets up tempeature the cylinders load up. There were no cutting or splicing , I popped 2 wires out that was for a serial wire and the other injecor and pinned it into the other connector.

[Czop418]

And about it , everything electrially work fine rpm's, mph , etc .... But the only thing is i cant diagnose anything i plug my scanner in and it wont read ****. Not even rpms or serial #

[Czop418]

corection it reads the serial but when i pull like tps and **** like that and rpm it comes up na and mayb the opti. But on fireup it runs fine no miss's or anything but when it gets up to operating temp , it runs real rough like 2 or more cylinders are loading up.

[ta350]

If you're splicing any data wires together you're making more problems for yourself.... having a crimp alone on a data wire even if its just if the wire broke is enough of a resistance to screw the signal let alone splicing two together..... so start there.

[V]

ok, im so lost here its scary..... alright... first off. by swapping the PCM(same as a ECU) to a lt1 version and using the v8 engine harness, you should have been good, the only real connections back to the body harness is for power and the diagnostic port. i honestly dont believe the BCM(body control module) cares if its a v6 or v8, i doubt they are engine specific. It seems the injectors loading up is a sign of them getting an improper signal and staying wide open, and you may soon hydrolock the engine. If the diagnostic hookup isnt workign properly start by getting that resolved and dont run the motor till you do, or you just run the risk of damaging it. I'd look at my lt1 and the harness that i have, and wiring diagrams if i had time but right now i just dont, (packing to come back to the states). I just suggest you get help from someone who knows more about wiring up a fuel injected motor, and itll probably turn out to be an easy fix.

as for swapping full body harness, it shouldnt be neccessary.

[Czop418]

If you're splicing any data wires together you're making more problems for yourself.... having a crimp alone on a data wire even if its just if the wire broke is enough of a resistance to screw the signal let alone splicing two together..... so start there.






There were no cutting or splicing ,



Not trying to be a douche but please read ALL the information before you post a reply.

[sweetbmxrider]

listen. stop.

remove the frankenstein harness from the engine bay. get the lt1's body harness that runs under the dash. route it in the swap car and plug in the front and rear harnesses. route the engine harness with the lt1's computer and plug it in.

[deadtrend1]

Not trying to be a douche but please read ALL the information before you post a reply.

The information you provide is difficult to follow and comprehend. You come here asking for help, he was trying to give advice and you tell him no. That takes balls.

Moving onward, it may be best to start over. You have the LT1 engine harness correct?

If not, I think my friend has one from a 95 sitting around still. Not sure though.

[Czop418]

Nvm about this thread im trying to explain it as best as i can but you gotta see it to understand it. Idunno Mods just close and delete this thread.

[sweetbmxrider]

http://www.tacreationsusa.com/3_4_3_8_v6_to_lt1.htm

http://www.v6conversion.com/homeframe.html

http://www.ls1tech.com/forums/lt1-lt4-modifications/1058012-v6-v8-swap.html

don't lock, just clean up

[Czop418]

Thanks guys. I really appreciate it but it seems everybody who did the swap changed out the whole body harness. I mean I personally am not the one who is doing the wiring , and i know the kid who is doesnt want to redo the whole body. My Main concern isnt the cylinders loading up , Mine is Why the scanner wont be able to pick up. It only reads the serial number and thats it. Any Possibility's why this might be happening. I mean All he did was re pin the data to a Hot. To give it power. If im correct.

[deadtrend1]

Thanks guys. I really appreciate it but it seems everybody who did the swap changed out the whole body harness. I mean I personally am not the one who is doing the wiring , and i know the kid who is doesnt want to redo the whole body. My Main concern isnt the cylinders loading up , Mine is Why the scanner wont be able to pick up. It only reads the serial number and thats it. Any Possibility's why this might be happening. I mean All he did was re pin the data to a Hot. To give it power. If im correct.

what kinda of scanner? A obd2 scanner?

[Czop418]

snap on scanner. And its obd1. I mean it could be his scanner. Because obd1 has 2 keys if im correct and his odb1 connector doesnt have the slot for the keys. So sometime this week , were going to have another friend bring home his scanner cuase his obd1 plug has the option for the key's.