Those words sound so familiar. Anyways, I figured out what I thought was the last of my issues today. (I had the coil signal wires ran to the wrong bank of cylinders...).

The motor is an '02 lm7; ls6 manifold/rails/injectors and the stainless works headers. It cranks fine and fires almost instantaneously now. However, as soon as it fires, it backfires and dies. I haven't hooked a 'noid light to my injectors but the plugs are getting wet and I have ~60psi off the rail at all times. My scanner shows an rpm signal(so I would presume good crank position sensor?), fairly accurate IAT and CTS temps, injector pulse width values and shows outputs from the o2s. Motor HAD bad grounds but I have added three more. The PCM is a red/blue from '02 truck that I had Vince @ Trifecta Performance flash with MAF, rear o2 and VATS delete and told him about the ls6 intake and injectors.

Help me out guys, where do I go from here?

 

My first inclination is to suspect the ECM programming, but I dunno for sure... Are you getting any codes??

I don't suppose you'd have a second, compatible ECM you could swap it out with...?

 

Honestly that was my first thought as well, but Trifecta has done a significant number of tunes with others without hiccups before... Maybe I'll call him tomorrow to see what he says.

No codes whatsoever. And a no on the second ECM. I bought it brand new from my work and now we don't stock them. hehe.

 

Well. Figured it out. I guess you could say it WAS programing. Emailed Vince and he said he double checked his logs and they say he deleted VATS. He also suggested that usually swaps like this (that he has delt with) do this when something it messed up with the MAF. Which startled me because I asked to have the MAF tuned out and run a MAP only tune so I had NO MAF or maf wiring. Picked up a brand new MAF from work, applied power to the MAF and signal to the PCM and it fires up no problem now. Holy crap is it loud. Side dump exhaust with no muffler inside a tiny garage. I'm happy. Tonight I'll dump coolant in it and hook up the last brake line and try to take it for a spin!

 

Right on man, congrats on the milestone!

 

Heads interchangeable between what? Again, intakes between what?

Man, this thread couldn't have come at a better time.

 

You mean, like ten months later?

 

No I'm just having a different crank, no start issue again! The only one since this thread!

 

hey iansane, did you do a whole thread on this swap? ive cloned my 91 firebird into a GTA and am now making my 5.3/T56 parts list to do this swap as well...

 

Nope. Not really. I had a "since I bought the car thread" in the firebird section but never really updated it. No digicam, no motivation to chronicle the craziness. Do you have specific questions?

 

i do now! lol, im buying an LM7 from work, do i need to be year specific on the engine concerning the mounting of it to a T56 from an LS1 F-body? Example, 03 or 04 LM7 bolted to say a 98-02 LS1 T56 (camaro or firebird)... does it matter? i heard the crank was different on certain LM7's??

 

I've only heard of the cranks being different on LQ4's, but I may not have heard everything. At any rate, you should be fine with an '03-up engine.

 

thanks 5.7, ive been reading alot of your posts about this and LSx related swaps, any tips or pointers? i'm compiling my parts list right now, i have the engine out back about 100 feet away that im looking to buy.... one issue im finding is an inexpensive accessory kit from an F-body... meaning less than 500 bucks

 

Check the truck engine link in the LS1 swap sticky.

Now,

 

five7 is right. Everything I've read has been in regards to '00 LQ4 motors having a difference length crank. But I always wondered if that meant you could use the LT1 trans/bellhousing/shat if you already had it... Would make upgrading easier in a case like mine where I already had an LT1 t56 behind my original 305.

And yeah, being an '03 you should be fine. My motor was an '03 so if you need any wiring questions answered, let me know.


Haha. No worries, the car starts now.


But I guess I forgot to mention why it didn't start. The pins backed out of the crankshaft position sensor and it basically received no crank signal. Swapped the pins with good ones and voila.