96 LT1 Stumble, Miss and Backfire

[keithr]

I have looked at previous posts and none have fixed what I'm dealing with. I pulled the engine last Sept. to do a full cage and new chassis. I should say at this point the engine ran flawlessly when I pulled it out, I'm running E85 with a D1 procharger at 15 pounds of boost and its rwhp was dyno'd at 617hp. That's why I had to put a cage in it! Well cage all done and installed the engine without the 4L60E and installed a full race 400 turbo with a brake, I removed the trans harness from the main harness and turned off the automatic in the ECM switch tables. Fired it up and it has a terrible stumble and backfire if you poke and don't let up, I thought it might catch up and run good but it didn't. I have replaced the O2's, the MAP sensor the Opti distributor, cap and rotor,I've unplugged the MAF and run it on speed density and still runs like crap. Thinking I may have done something to the tables that was wrong, I reinstalled the tune with the 4L60E in it and runs the same. I'm running a fuel cell (same as last year) with an Aeromotive A1000 pump and an Areomotive boost sensed fuel regulator, it idles at 46psi with 80lb injectors. Nothing has changed except putting the cage in and running motor plates front and rear, I have checked all grounds and even run a wire from the engine to the frame and then to the ECM,"no change". I don't know what to do next Please help! I have Data logged it and no codes and everything looks normal............Sorry for the long post:cry:

[firebird_1995]

its a long shot but are you running a knock sensor? the motor plate could be allowing vibration to trigger knock retard.

[MEAN LT1]

Are you able to datalog at all?

[keithr]

I am, I'll look into that! Can I disable them completely?

[keithr]

I have data logged and everything looks normal according to Bryan Herter at PCM for less

[96LT1355Z28]

Have you checked all the simple stuff? Plug gap (if you replaced plugs), plug wires are good and on the correct plugs? I checked twice and sore the wires were on the correct cylinders and until I got under the car and followed each wire I didn't catch I had two switched.

[keithr]

I have isolated the knock sensors, no change! Removed the fuel filter and installed new one, still no change, I have pulled all the plugs and checked them, they only had a half dozen passes on them. Turned ignition on and have battery voltage at all the injectors. Have Data logged it and no DTC's. I'm out of thoughts and ideas, any other suggestions would be welcomed, or any LT1 guys in the Colorado Springs area that have good knowledge of these engines would also be welcomed. Thanks!