LS6 Power Issues

[Mgodsy]

Hi everyone,

I have a 1968 C10 that I have done an LS6 conversion out of a 2004 Z06 corvette and an 4L60E trans out of a truck.

The problem I'm experiencing is that when the engine is in park it runs good and has good throttle response. It sounds like a beast. But, when I put it in drive and give it gas it cuts out so bad that the truck will hardly move. I get no trouble codes on the scanning tool.

I'll list what has been done to try to make this simpler,

I purchased the LS6 with the computer and wiring harness. I sent the harness and computer out to be configured for my truck. The company that did the wiring and programming also changed the throttle from DBW to Drive by Cable and I changed out the throttle body to a drive by cable.

-I have replaced the plugs and wires
-Verified firing order
-Verified fuel pressure at star, under load and at idle. Consistent 58psi
-Changed fuel
-The new wiring harness only has 4 wires for it to run: fuel, key on power, constant power and fuel pump. Also has a ground. I verified the wiring was hooked up correctly
-I get no trouble codes on scanner


Again, when the truck is in park sounds like a beast, as soon as I put it in drive and give it gas it just falls on it's face and barely has enough power to move the truck. It runs very rough when in drive and giving it gas.


Any help will be greatly appreciated!!!

[BR3W CITY]

If it runs fine while still, but stalls when put into drive, check if your running an NSS sensor. If your not, then the idle needs to be turned up slightly because the engine load changes, but the engine itself might still be shooting for a very low idle.

[Mgodsy]

Thank you for the help.

I do not have a nss being used. The engine runs great when in park or neutral the problem happens when I put in any gear. It idles great in gear but when you try to give it gas it cuts out terribly. It's like I unpluged 4 of the cylinders. Put it back in park and it instantly runs great again.

[Mgodsy]

I have a fuel gauge attached to the fuel rail and it is at 58psi when I give it gas while in gear. It did drop to 50 psi when I floored it but just for a second or so then went right back to 58 while under load.
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[Heavymetl]

???

Who did the drive-by-cable conversion? If the PCM isn't capable of supporting an IAC then that's your problem.

[Mgodsy]

Thanks for the help Heavymetl.

I've contacted a local programmer and will be taking the computer to him to validate the programming is correct. I'll let you know if that fixes it.

Thanks,

[White knuckle Garage]

it could be your DBW conversion or something as simple as a intake gasket. on the DD i started having trouble like you talk about when you first give gas and hooked to a computer as soon as the pedal depressed it was causing a miss fire due to a bad intake gasket. problem fixed for $40 with parts from local bussiness